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MONTHLY REVIEW

Published by the American Electroplaters Society
Publication and Editorial Office 3040 Diversey Ave., Chicago

VOL. XVI   JUNE, 1929   No. 6

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EDITORIAL

So much has been printed on the subject of taking an interest in the work of the electro-plating industry as sponsored by the American Electro-Platers’ Society and attending the branch and annual meetings regularly; the role and value of the more or less silent ”side liner, ”the efforts made to secure attendance of all the members at least several times a year and so, there seems but little left to say.

The fact is that there is a great deal more education in regular or less frequent attendance than those who stay away ever realize. A full realization of this would come to those members if they would only attend and associate with the regulars, and then after thus spending a pleasant and educational meeting discover that, mere attendance becomes an enjoyable service in itself.

Even though members feel that they are not apt for active floor work, their presence adds incentive to the member who has this faculty of expression, and soon by this method of observation becomes full of vim and adds enormously to the interest and encouragement of the branch officers ”who labor to please you.”

When a member has done at least that much for a while and can call ten or twelve regulars by their first names, and can take part in the current conversation and the experiences encountered in our business, he is finding a niche congenial to himself and in accord with his duty to the industry that provides his living.

We all joined this society because its ideals, teachings and activities appealed to us; why not get some good out of it, and give it your moral and support ?

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CHARLES PROCTOR, FOUNDER OF OUR SOCIETY*

*Read at Annual Convention, Toronto, Canada.

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This short paper I am going to present to you this afternoon includes my own personal opinions and investigations I have made during the past few months. The title of the paper is ”The Present and Future of Chromium Plating, a Call to Arms in Defense of Commercial Chromium Plating in America. ”I am not going to discuss the anode question. You have heard enough of that, and if a man doesn’t know he had better study the matter up and find under what conditions of temperature he will get the best results. As far as anodes are concerned we get splendid results with lead anodes. We get splendid results with steel anode, and with lead and steel, and we get splendid results with chrome steel anodes with possibly ten per cent lead anodes in solution, so it is not necessary for me to discuss those matters. I want to bring something before you that may be of interest to you because the future of chromium plating may depend upon what I have written in this paper.

”At the annual banquet of Newark Branch, A. E. S., I presented a paper entitled ‘The Past, Present and Future of Chromium Plating.’ My paper today is ‘The Present and Future of Chromium- Plating, a Call to Arms in Defense of Commercial Chromium Plating in America.’

”It is unnecessary for the purpose of this paper to go deeply into the past of chromium plating in America. All that is really necessary is to assemble the facts upon which the priority is based and eliminate from consideration for all time the numerous patents that presume to control the destiny of chromium plating in America and force upon the metal fabricating industry unwarranted financial burdens for at least a decade and a half or until these patents have expired.

”A substantial majority of manufacturers of metal goods in America have fully decided that they will not pay for the right to use a process or processes long since public property and they are prepared to defend their rights in court if necessary.

”Sargent’s work was published in 1920, many years after he had completed his research work, which was in part financed by Carveth and Boncroft. Sargent was the first author of a defined proportion by weight for a chromium solution as follows: Water, 1 liter, or 1 gallon; chromic acid, 245 grams or thirty-three ounces; chromic sulphate, 3 grams or 1/2 ounce; concentrated sulphuric acid five cc. 3/4 ounce, plus or minus.

”There is not a man in the audience that can state that the present chromium solution does not measure up to Sargent’s solution plus or minus.

”The chromium solution advocated by the author is almost identical with Sargent’s solution except that chromate of iron is added directly to the chromic acid, when being dissolved at near the boiling temperature.

”The minimum solution advocated by the author is: water, 1 gallon; chromic acid,16 ounces; chromate of iron, 1 ounce; chromium sulphate, 1 ounce; concentrated sulphuric acid, 1 cc.

”The advanced steps should be upon the same proportionate basis up to sixty-four ounces of chromic acid, the thirty-two ounces basis, however, has been found ideal in the automotive industry.

”From the commercial standpoint there are three important factors to consider which have determined that chromium plating in America is a commercial process.

”First, the patent of Placet and Bonnet of Paris, France, U. S. Patent No. 526, 114, dated September 28, 1894, which expired in 1911 and therefore became publicproperty. Any factor mentioned in this expired patent can be used to produce a commercial chromium solution based upon the use of commercial chromic acid which they advocated. Its value was substantiated by Carveth and Curry in 1905.

”Placet and Bonnet in their patent also mentioned Ferro Chrome Anodes. Some of our present-day commercial chromium solutions are absolutely controlled from the anode side by this type of anode.

”Ferro chrome anodes in the form of chrome steel anodes can be used and are used with the solutions mentioned and ferro chrome anodes were mentioned in the expired patent of Placet and Bonnet.

”Lead anodes are used extensively. Some operators use antimonial lead anodes, claiming that this type of anode does not coat over, with lead chromate as readily or as adhesively as when lead anodes are used without the antimony addition.

”One of the corporations which controls a number of patents covering chromium plating also claims lead anodes as part of their patented process

”Lead anodes were patented in Germany Patent D.R.P. No. 105,847, September, 1898, also expired in 1915. Knowing this to be true do you think there is any earthly reason why you cannot use lead anodes or chrome steel anodes with Sargent’s solution or the solutions outlined by the author?

”You can purchase a photostat copy of the German patent referred to from the patent office in Washington, D. C. for seventy-five cents.

”I believe every plater in this audience will desire to obtain copies of the herein before-mentioned expired patents. They can be obtained from the U. S. Patent Office.

”There are two other vital factors, however, in connection with chromium plating as with any other type of electroplating solution that must be considered and reduced to a standard basis. Current and temperature control, when you know these factors, and adjust them to your own individual plant requirements, then with the solution formula already mentioned you know all that it is necessary to know about commercial chromium plating or patented chromium plating as it is known today.

”I desire to mention one important factor recently mentioned by Schneidwind of the University of Ann Arbor, Michigan, a gentleman whom you all know so well from his splendid work entitled ‘A Study of Patents Dealing with the Electro-Deposition of Chromium,’ the Magna Charta of Chromium Plating which has enabled you to a declaration of independence. No taxation upon commercial chromium plating in America.

”The factor is kerosene oil. This material when placed on the top of any chromium solution acts as an inhibitor and prevents the hydrogen and chromic acid sprayresulting from the excessive hydrogen gas evolution at the cathode from being carried out of the solution.

”From experiments the author has made upon a limited scale with kerosene it would appear that all the costly apparatus not installed to carry off the hydrogen and chromic acid spray so detrimental to the plater’s health can be eliminated by its use.

”There are apparently no detrimental results upon the cathode chromium deposits as the hydrogen acid evolved at the cathode cleanses the kerosene oil from the surface and permits normal deposits.

”Inhibitors are well known in many branches of the metal fabricating industry that must pickle their product with hot sulphuric acid pickling solutions to remove fire scale.

”Lignone, a by-product in the paper producing industry, is universally used for the purpose in powdered and liquid form. It forms a blanket upon the surface of the pickling solution, keeps the hydrogen down below its surface and saves acid and steel.

”Every plater should try our kerosene oil and determine its real commercial value. A depth of one-fourth of an inch is ample for the purpose. So ends the present of chromium plating. The next step is towards the future.

”The majority present must of necessity agree that chromium plating is an established commercial process and as such can be practiced at will. Nevertheless, an action for infringement has been started in the U. S. District Court, Corporation of Indianapolis, Indiana, against one C. Roy Gleason, of Chicago, Ill.

”It would now appear that C. Roy Gleason, the defendant, is in the employ of the Vacuum Can Company of Chicago, and that one or more of the officials of the Vacuum Can Company are officials of the General Chromium Corporation and incidentally the United Chromium Corporation, the holding company.

”You can readily realize how important it is to the commercial chromium plating industry to have this suit tried out on its merits. Should the Metals Protection Corporation win its case on default or through a weak and improper defense, it is reasonable to assume that the General Chromium Corporation would eventually absorb the Metals Protection Corporation. The road would then be closed and the commercial chromium plating industry-would be enchained until the patent in question expired.

”Mr. Gleason should be put on notice that the commercial chromium plating industry of the U. S. expects him to defend the suit in question on its merits and that no subterfuge or default will be permitted. The commercial chromium plating industry stands ready to assist Mr. Gleason in his defense by submitting all the proof at its disposal which, if properly presented to the court, must of necessity substantiate the claims of the industry that commercial chromium plating can be carried on without infringing any valid patent

”Some of the largest manufacturers in the U S have practically decided to form the chromium platers protective association of America, in which event the legal talent of this organization will be in position to defend the rights of the commercial chromium plating industry.

”Every manufacturer in the U. S. that is now chromium plating commercially should contribute to this great protective organization to protect their interests and the interests of American industry.

”This, then, is the future of commercial chromium plating in America. You, whose interests are at stake must be the determining factors as to whether this future shall be yours and controlled by you. ”(Applause).

MR. ALLEN: Do you know of any patent covering temperature control or the current density?

MR. PROCTOR: I do not. So far as the paper is concerned, you have learned the intention of that paper. I merely mention a solution that I haven’t given out that is being used very extensively, and I don’t think there is any need for discussion. It remains with you to be the factor to decide what you want to do.

PRESIDENT FEELEY: Having completed Mr. Proctor’s paper, and there being no discussion of same, we will not proceed to the paper of Mr. Van Derau. (Applause).

MR. C. VAN DERAU (Supervisor, Finishing Depts., Westinghouse Electric Products Co., Mansfield, O., ”Engineering of Chromium Plating ”): I feel somewhat like a piker coming up here today without a paper. There is a reason for that. Now, I had all the good intentions in the world of presenting a paper as well as exhibit for this convention, and I took as a title ”The Engineering of Chromium Plating. ”At the same time I thought as an exhibit that we would take photographs of automatic equipment with our former hand rates and our machine rates, at the present time, showing what can be done with automatic equipment throughout the whole of the finishing industry. It so happened that on May 7th Mr. Farber, who has been connected with our plant as a chemist and who naturally carried on a lot of these tests and researches, as well as special development, was taken over as a research associate of this Society at Washington. That was one thing that prevented going farther with the paper. Then on May 21st I was given a little more latitude to cover at the plant. As a matter of fact, whereas formerly I was at the head of nine different departments throughout the plant at that time it was raised to twenty-nine.

Now, I have had my hands full and I have not had time to prepare a paper and for that reason I am offering an apology for not coming up here with a paper as well as exhibit. I had all the good intentions at the time I made the promise. One thing I will say, that we will have a paper and an exhibit at next year’s convention because we are going to start in plenty of time and what we miss by having it this year we will try to make up for next year.

There is one thing I might stress; in the way of general remarks as regards chromium plating. Now, there are three important factors in chromium plating. Most of them have been stressed this afternoon. There is one that has not been stressed and that is really part of the engineering of chromium plating. That is the proper design of plating rods. Practically every plant that attempts to chromium plate finds that they can get plates on some portions of the work but they have trouble getting in the recesses and things of that kind. That is simply a problem of current distribution, that is not a problem of solution. That is not altogether a problem of temperature. That is not all a problem of current densities as it is carrying that current to the point needed.

Now, it is more or less of a well known fact that current will jump the shortest gap. In other words we take a spark plug in an automobile and make one gap a sixteenth of an inch on one point and another a quarter of an inch, at what point does that current jump, across the wide gap or the short? That same thing is true in chromium plating, and the reason you can build up chromium with edges and for instance, we will take an object of this shape, going in that direction, it will present trouble, to get a uniform thickness of chromium at this point. We find we plate that with flat anodes regardless of the distance, we will build up a heavier plate, possibly an inch or an inch and a half back from this edge. Back in here we have a mere shadow of a plate. The reason for that is this: that the current is leading off to the shortest routes and not leading back into that recess and if there is any way of putting that thing in a glass jar and observing the gas bubbles being given off you find there is a tremendous liberation of gas here but few at this point. Now, the problem then is how are you going to conduct current back to this point, and that is the thing that appeals to the ingenuity of the plater or again becomes an engineering problem as to how to conduct that current to that point. Now, that means special racks, and, that means for instance going to a reflector or an object of that shape. The first theory was the anode had to be the same shape as this piece. That is not true. As a matter of fact you get the same condition with an anode of that same shape as you would with a flat iron. The only thing is you may throw in another half inch or an inch farther, but if you pull hack the point of this anode to within an inch of that recess and pull off here anywhere from two to four to six inches depending on the shape of this piece, you are widening this gap and you are making that current lead off the point of that anode.

Recently some of the things that Mr. Farber worked on and was developing were special racks. I want to tell you this; we plated a good many pieces for other people to see what we could do with them. In other words, we had glass molds that the company that was making them came to us and wanted to know if we would help them out. We have no axe to grind in the matter, we get nothing out of it, but we told them yes, we would do one, we wanted the experience, and we wanted to see how common this racking problem was in chromium plating. We took that glass mold with the ordinary tumbler and the problem was to get the same thickness of chromium in the bottom as up here.

Now, following ordinary plating practice we would take and put a round lead anode or steel anode or anything conducting current down in here and might have equal distribution at the top, might have it at the bottom, and when you get up there you find you have twice as much here as down here. Now, try to picture drawing that glass out of those glass molds by driving them out with air What happens? They stick, can’t get out. So we took that glass mold and made a very common rack, two pieces of board with lace cut-outs in to set the dye down in to hold them together, we came up here with a rod, down the anode and tapered that from a small taper to like this, flared it out to the end of the corners of the mold. We did not spoil any. We got the first one.

Now, that thing brings back to us again the importance of studying the design of racks. A short time ago a company in our city that makes lock washers wanted to chromium plate one of their lock washer dies to see what it would do. They did not want the expense of an installation to try out one or two dies, and they brought it over. All they wanted was the inside of the die, they didn’t care about the outside. So we rigged up a rack for that by putting a clamp over and clamping off an anode right to that cathode rack insulating with maycarda and a little rod run right down the hollow spot there, and I would say the area of that anode as to the cathode area would be something like forty per cent.

Now, again, we were successful and we were following out exactly the same theories we found out on other pieces of apparatus.
Now, then, the first thing that led us to that belief that it is one of the biggest stumbling blocks the average plater goes up against in chromium plating and that he wastes a lot of time experimenting with solutions to try to make them work, when it is not always that, if he could distribute the current.

Here is a big generator We will say we want to generate 220 volts d. c., it can be any figure, up in the thousands. We start it up at a certain speed and it generates 250 volts. We have no way whatever of controlling that. We wouldn’t get the same results at 250 volts we get at 220 volts, so there is a rheostat put in there and as soon as the thing jumps at 250 what do you do? The man goes over and turns the rheostat and regulates the current flow. The same thing is true of these odd shapes we get in plating that we have got to regulate the direction that we want the current to go in. It is not so much plating solutions but it-is in the technique of application. That is the thing we have got to work with and it is the thing that we term engineering of chromium plating, and I don’t believe we can stress it too much.

About a year ago one of the colonels from the War Department working on aviation engines was a friend of the works manager and wanted to know if he could get an engine head chromium plated. What part of it? The combustion chamber. ”Can you chromium plate direct on cast iron, can you on this combustion chamber ? ”

”Don’t know, we will try it.”

Now, Mr. Farber and Colonel Prentice worked for eight hours trying to get a spot of chromium that was not as big as a point of a pencil down in there. We turned back and instead of going to work and doctoring that plating solution, instead of switching the temperature, we knew would give certain results on other work, lowering it or raising it, we switched the current. We had switched the current all over the map We started to study the anode, and current distribution, and took our anode surface by cutting out a piece of lead about the shape of that combustion chamber and I might say it was a Ford head, two Chryslers, a Hupmobile and a Whippet we ran all together. We had to cut out different shapes. We put them on a solid lead sheet. We started out with this Ford head. That was the hardest one of the bunch to finish up, due to two little pockets there where we would get gas pockets or solution displacement. We got fairly good results with the exception of those little gas pockets in our next attempt and were able to run that and ran it to two-thousandths chromium on the inside of the combustion chamber. One of the things it brought out the possibilities of combining anode and cathode racks together. When we think of plating we generally think of anode rod here, one here and a plating rod run through the center and the rod we make flexible as a rule is the one in the center.

Now, that is wrong. The rods we want to make flexible are the anode rods. That is engineering again, so that is a comparatively easy thing to do. Clamps welded on the buss bars, and by elevating the main busses up over that so we could slide the anode rod back and forth we were able to get away from that.

After we had done that we came to these heads and we found that by putting a sheet of macarda over the plain surface of that auto head, we insulated that all from plating because we broke that flow of current right into those points which would be the high points in that case, and shaped our anode by twisting it around and drive it right down within one-quarter of an inch at the lowest part of that cavity and tapered off and we got the next six heads without any trouble.

On the Ford Head these two little gas pockets, we did not know how to get away from, so we followed it up and stuck two tacks into that head to drive in to those little pockets and that part of it was over. Then there is another trouble, current distribution, and the sooner we recognize that as being a thing we have got to learn to manipulate just like we had to learn to manipulate rheostats or other plating tanks we are going to commence to chromium plate anything they bring along. That is one of the biggest things the plater has got to master.

I brought photographs of one rack. I have got a good many I expected to present here and was prevented from it That is a combination anode and cathode rack. There are one or two pieces on here and if you look you will see there is a terminal guard that would be almost an impossibility to drive chromium in there, without burning the points so we have combined here and run a little steel wire up in that and this bar that runs there is a clip that snaps on to that as you go into the solution that drives the current up into the cavity or that round terminal. Between that is a sheet of macarda, with macarda tubes to prevent the screws from short circuiting that rack We will be able to plate anything in chromium regardless of the recesses as long as we give this real consideration and quit looking for a magic powder to give us this increased throwing power we expect in chromium solutions

Here are one or two other types of racks. They are the first racks, they are not the racks in production. We put two more pieces on that rack but there are the ones. I might say that this is Mr. Farber’s idea. Iron bottoms, for instance, we could plate them one at a time. We can’t charge the people fifty or seventy five cents more for that iron. That has to be done cheaply. When you think of the whole finishing cost in one iron it is ten cents labor. We can’t put twenty-five more on it just to chromium plate it; we have to get something that will cost us one or two cents. That means we have fast production, methods for handling the material quickly.

You hang them in the tank like this, here are your fadiuses, fifty-eight degree bevels. Do you think the current will go around like that? If you don’t believe it take any kind of’ plating and see if your corners are not heavy.

By putting a swivel in the top of the rack that can be turned a quarter turn, half ‘way through that plating cycle of five minutes, like that. You can put two racks in there and as you come over drop two in, turn two of them a quarter turn and take the next two out. If that is not a working cycle I don’t know what you can get; that shows the idea there and the thing works out well for a great many pieces particularly where you want to turn and drive the edges instead of the bottom without breaking contact with the chromium plating solution.

That calls for close study, a little bit of cutting and trying and after all what is engineering? Cutting and trying, then after they get a thing working, standardized on that point. That was the thing I hoped to bring out in the paper that I couldn’t give and I have only briefly touched on the possibilities of it.

There is one other thing I would like to say before closing regarding chromium solutions or things we have found in the past year. Dr. Blum at last year’s convention had a statement that as long as chromium solutions contained approximately ninety nine per cent chromic acid and twenty-one per cent of chromic sulphate they would produce satisfactory chromium deposits. At that time we recommended a solution of sixty ounces of chromic acid, commercial chromic, and two ounces of iron, chromate without any additions of sulphate. I want to retract that today and it is necessary to add approximately one-half ounce of chromic sulphate or sulphuric acid or some of the other sulphates to bring up the sulphate content. We were right at the time we made those other deductions, for this reason: that the chromic acid as furnished by the suppliers at that time was approximately one per cent sulphate. Due to the increased use of chromic acid they have gradually been refining, getting pure chromic acid. You are getting commercial chromic acid today that is equivalent to c. p. chromic acid of five years ago. Our source of supply has changed. We built up a new solution of about 500 gallons and we switched over running reflectors in there, and commenced to get streaks, just a little hair line streak down the bottom of the reflectors that wiped off. These looked as though you tried to oxidize them, green, purple, brown, yellow, every kind of color. It was as if you had dipped them in a hyposulphide oxidizing solution. There was a new chromic acid solution. Mr. Farber said it was lower in sulphates than our old one was, and to let us check it against the other one to be sure, so we tried them out in the old solution. It worked. I said this is another chance to prove up the things Dr. Blum told us at the convention on the basis of ninety-nine one. We will add enough sulphate to bring it up to this point. We added enough to bring it up to the one per cent, and I want to tell you action was instantaneous.

From that time the streaks disappeared and we have had no appearance of streaks since. That illustrates that Dr. Blum or Mr. Haring, possibly, who carried on the experiments, have absolutely: brought out a point that is vital to successful chromium plating. Thank you.

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A PAPER ENTITLED
“ TEMPERATURE CONTROL”

To Be Read by Mr. A. W. Chase, of the Foxboro Co., Inc., Foxhoro, Massachusetts

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”Automatic Temperature Control. Introduction. In this paper we will briefly discuss the following questions relative to temperature control:

1. Why is temperature control necessary?
2. How does a temperature controller work?
3. What to look for in the selection of a controller.
4. Who uses temperature controllers?
5. What will a temperature controller do?

”Why is Temperature Control Necessary? Temperature control is so well established in practically every industry today that the question ‘Why is temperature control necessary?’ is seldom asked. If we attempt to answer that question a great many answers will be found depending upon the particular operation under consideration. An analysis of these various answers will undoubtedly resolve itself into two fundamental reasons for temperature control.

”The first is this: the rate at which a reaction takes place is doubled for every increase in temperature of approximately 10° C or 20° F.

”A practical illustration of this statement is to be found in the pickling of steel. It is the practice of one steel company to maintain a temperature of 160° F. in a fresh batch of pickling acid. The steel pieces being pickled are kept in the tank for an indefinite length of time. As the acid is used up and becomes weaker, it does not have the same effect on each batch of steel in the given length of time. In order that the work may move forward at a definite rate, the time of pickling is kept constant but the temperature is increased a few degrees in order to obtain in the allotted time a pickling action equivalent to that caused by the original acid at a lower temperature.

”The second fundamental reason for temperature control and one which is more or less related to the first, is this: for practically every industrial process involving the use of heat there is an optimum temperature; that is there is one temperature or narrow range of temperature best suited for the particular process. At first glance it would seem that this statement is in conflict with the previous statement but it is due to the physical and chemical properties of the substances involved in the reaction which impose a limit to the temperature at which the process can be carried on.

”In the manufacture of Crisco or other lard substitutes of this nature, vegetable oil, such as cottonseed oil or peanut oil, is mixed with finely divided metallic nickel which has been reduced to the metallic state from nickel oxide by heating the nickel oxide in an atmosphere of hydrogen. By bubbling hydrogen gas through this oil-nickel mixture, a chemical reaction takes place which results in the Crisco, found on the shelves of all our grocery stores. In keeping with our first statement, the reaction rate increases as the temperature is increased up to a temperature of approximately 360° F., but beyond that temperature, because of certain decomposition products resulting from the burning of the oil with subsequent bad taste in the product, the reaction rate does not increase but instead, actually decreases.

”There are usually special conditions surrounding the operation of each individual process which require operation at one specified temperature or very narrow range of temperatures, which after all is the basic reason for temperature control, and any process which is capable of manual control can be controlled much better automatically.

”How Does a Temperature Controller Work., In answer to the question, ‘How does a temperature controller work?’ an attempt will be made to describe briefly the operation of one of the best and most widely known automatic temperature controllers on the market today.

”This controller consists of two principal parts, first, a temperature measuring element, sensitive to the temperature changes in a process; and second, an air mechanism operating a valve which controls the admission of the heating or cooling medium to the process through the action of the temperature element. The thermal or temperature-measuring element is a closed system consisting of a sensitive bulb, a helical tube and a capillary tubing connecting the two

”There are two types of thermal systems, the vaporization and the gas filled types. In the vapor tension type of instrument, the sensitive bulb is partially filled with a liquid which exerts a vapor pressure as the temperature surrounding the bulb increases; this pressure is transmitted through the capillary tubing to the helical tubing to the helical tube, which unwinds. The pen and pen arm, suitably attached to the helical tube, record the temperature on the instrument chart.

”In the gas filled type the complete thermal system is filled with an inert gas, the pressure in the closed system increasing in proportion as the temperature surrounding the bulb increases.

”Let us assume that we have a heating operation such as any hot plating solution in which case we should have what is known as a direct acting valve in the heating line. The direct acting valve is normally closed by a spring and requires air pressure under the diaphragm motor to raise the valve stem, permitting passage of the heating medium. Now, there is in every Foxboro controller a very ingenious little device known as a control head, which in this case allows the passage of air from the air supply through this control head to the diaphragm motor, holding open the valve until the required temperature is reached. When the index arm is set at the required temperature on the chart by means of the outside setting arrangement, a small air nozzle which moves in direct relationship to the index arm is also set at a definite point.

”Now, this small air nozzle is connected to the control head by means of a fine capillary tubing and a small amount of air is allowed to bleed through this capillary tubing and air nozzle. Rigidly mounted to the same axis about which the pen arm rotates is a flapper mechanism which moves in direct relationship with the pen arm. This is also the axis about which the index arm and air nozzle rotate. When the temperature for which the controller is set has been reached, the flapper just referred to covers the orifice in the air nozzle, through which a small amount of air is escaping from the control head. When this air leak is stopped, a small diaphragm or metal bellows expands under the increased pressure built up in the control head and unseats a small pilot valve inside the control head, allowing the air to spill out into the inside of the controller directly from the control head, and at the same time this small pilot valve seats in another position and cuts off the air to the diaphragm motor of the controlled valve in the heating line. The spring of the valve closes the valve and the flow of heating medium stops.

”With the flow of heating medium stopped, the temperature in the tank drops, the gas or vapor-pressure in the sensitive bulb decreases, the helical tube contracts slightly, draws the flapper away from the air nozzle, allowing the air to bleed from the metal bellows. This causes the diaphragm metal bellows to return to its normal position, reseating the small pilot valve in its original position and again permitting the air to pass to the diaphragm motor, which opens the controlled valve, admitting heat again to the process to maintain the proper temperature; and the cycle repeats itself over and over again. This is what is known as a single-action controller.

”In the Duplex Temperature Controller which is necessary on chromium plating tanks to control both cooling and heating medium, the mechanism is practically the same, except that there are two index arms with an air nozzle moving in conjunction with each and two flappers moving in conjunction with the pen arm The two index arms are set slightly apart, and the amount of temperature difference between the action of the valve in the heating medium and the action of the valve in the cooling medium depends upon the size of this gap between the two index arms. When the temperature reaches the point at which the first index arm is set, one flapper comes against the corresponding nozzle and causes the closing of the valve in the heating line. If, due to the process, the temperature rises to the point for which the other index arm is set’ one flapper closes the air nozzle, which in this case operates the diaphragm motor to open the valve in the cooling line to keep the temperature within the desired range. About ninety of these duplex controllers are being used on chromium plating tanks.

”Special Points for Which to Look in the Selection of a Controller.—In the selection of a controller there are a number of types from which to choose, such as the self-actuated, the steam operated, hydraulic-operated, electrical and air-operated. Where rough control only is desired, a self-actuated or steam-operated instrument may be sufficient, but where close control is required it is an admitted fact that air-operated control is superior to all other types. By air-operated control is meant a mechanism using an auxiliary air supply as motive power to actuate the controlled valve such as has just been described. Air is one of the most reliable and flexible of motive powers. No satisfactory substitute has ever been found for certain pneumatic devices such as air brakes, for example. Leaks may develop in the air line, but there is always a sufficient volume of air to operate the device. In steam and hydraulic lines leaks mean dripping moisture. A break in an electrical system puts the apparatus temporarily out of commission. If an air supply of fifteen pounds per square inch is not available, the necessary volume of air to operate the controller can easily be obtained by a small motor driven, belt driven, or steam driven compressor. For reliability the air-operated controller should always be chosen.

”Another important point to verify in the selection of a controller is the relation between the motion of the thermal element and the temperature range of the instrument. No one will dispute that mechanically multiplied motion will magnify any error. It follows therefore that it is desirable to have the motion of the actuating element per unit change in temperature as large as is practical. For example, if the thermal element in one controller expands .5 inch for a change of 100° F. and the element in a second controller expands only .1 inch for a change of 100° F., it is a simple matter of mathematics to determine that a motion of .001 inch in the first controller is equivalent to .2° F., whereas .001 inch movement in the second controller is equivalent to 1° F. Now, if in the calibration of these instruments there is an error representing the movement of .001 inch, or if the calibration should get out of adjustment, it is perfectly obvious that the error in the first instrument would be only one-fifth as great as the error in the second instrument. An instrument having a relatively large amount of movement in the thermal element is nearer inherent accuracy and will remain in permanent calibration longer than any other type.

”On plating or any other important process work it is always desirable to have a record of temperatures even with a controller; the temperature recorder controller, which combines both recording and controlling features in one instrument, meets this requirement perfectly. It goes without saying that the controller should be capable of being set at any temperature within its working range and be repeatedly reset to any one temperature for duplicate results without requiring constant adjustments. The highest grade controllers have an outside setting arrangement whereby the index arm can be set at any definite temperature by merely turning a key similar to a clock key. The controller should have a certain amount of ruggedness, but this feature should not be carried to the extreme at the expense of sensitivity. Within practical limits the simpler piece of apparatus is always the best. Therefore, in the selection of a controller, keep these points in mind: reliability, accuracy and permanence of calibration, ruggedness, sensitivity and simplicity.

”Who Uses Temperature Controllers?—The widespread use of temperature control is comparatively recent. It is a matter of experience that an industry will ordinarily go through a very definite cycle in using industrial instruments. First, the indicating thermometer is adopted. This gives a momentary indication of the temperature which is always available when a reading of temperature is desired, but it leaves no record of past performance. Then follows the adoption of the recording thermometer, which tells not only the temperature at the time of the reading, but also gives a complete history of the temperature during the process up to that point and opens the way for reproducing those temperatures or temperature cycles which show the best results, under a given set of conditions. This naturally leads to the eventual adoption of automatic temperature controllers which make it possible to duplicate automatically that which has been previously controlled by hand; and, of course, if a recorder controller is used, a record of the control temperature is also obtained at the same time.

”Today there is hardly a trade or industry which does not use temperature control at each critical point in the manufacture of its product. Take some of the basic industries for example: the petroleum industry has been one of the most aggressive and progressive users of temperature controllers, and incidentally of other types of controllers as well. In the production of gasoline, naphtha, kerosene, gas oil, fuel oil, lubricants and other petroleum products, temperature controllers have enabled the engineers to refine crude oil so as to obtain the highest yield of the more valuable products; without controllers the oil refineries would be helpless.

”In the lumber industry the modern dry kiln operator who wishes to put out a properly dried lumber is equally dependent upon a humidity recorder-controller to control the temperature and humidity in the dry kiln, and thus avoid case hardened lumber or otherwise improperly seasoned timber.

”In the canning industry, particularly in the state of California, where a very rigid state inspection is maintained, temperature controllers are indispensable in maintaining the proper temperature of the canning retort within 1/4° F. to properly sterilize the canned goods and to kill the bacteria, which would otherwise result in a poison food.

”In a very much younger industry or rather a new branch of an old industry, that of textiles, the temperatures in the manufacture of rayon are so critical that practically every step is controlled by automatic temperature controllers in order to produce rayon of a suitable grade.

”Within the last year or year and a half there ha:, been a phenomenal increase in the use of chromium plated materials, and platers have been using temperature controllers on their chromium plating tanks. The success of commercial chromium plating has been based in part at least upon close temperature control.

"Chromium plating, however, is not the only place where temperature control can be used even though it does hold the foremost place in the interest and attention of platers at the present time. On hot nickel and hot copper plating solutions temperature controllers are being used in increasing numbers. In addition to the application on plating, tanks, controllers have been used on alkaline cleaning tanks, pickling tanks and on rinse water tanks; in fact, controllers can be used to advantage wherever a steady operating temperature should be maintained, which means practically every operation carried on in the plating room.

”What Will the Controller Do?—Temperature controllers can conserve time, labor, material and power. In one respect, at least, the plater has one thing in common with all other workmen, that is, he is expected to produce the best work for the least money, which means, of course, the most work in the shortest possible time with the least expenditure of labor, materials and power, and always to produce a uniform product. Temperature controllers will assist the plater to accomplish this result.

”To prove this it is only necessary to cite the experience of the Foxboro Company itself. A number of years ago when the present plater, Mr. Shepard, took charge of The Foxboro Company’s plating room, there were no controllers on any of the plating tanks, rinse tanks, or pickle or cleaning tanks. After Mr. Shepard had been with the company a short time he began to realize that the situation was rather amusing, here was a manufacturer of controllers advertising to all different industries, telling everybody that they should use controllers on their various processes, and right there in their own plating room not a single controller in use. Mr. Shepard had had a number of experiences which proved to him that the installation of temperature controllers on the various tanks in the plating room would save the company considerable time and money; for instance, he states that before the installation of the controllers he was called away from the plating room one day only to return and find the room in a cloud of steam and the potash solution boiling over the side of the tank. Whether some one had turned the steam valve open a little wider or the steam pressure had been increased, no one seemed to know, but there was the potash solution over all the floor, representing a certain amount of money in the form of chemicals gone to waste and power also uselessly wasted.

”At another time a similar thing happened, except that this time it was a copper plating solution which boiled over into a nickel solution adjacent to it, which was entirely ruined and had to be thrown away. Here again was a useless waste of chemicals which, could have been prevented, had controllers been used. In addition to this it usually took some time for the tanks to come up to temperature in the morning before any work could be started.

”It wasn’t long before Mr. Shepard secured the opportunity for which he had been waiting because the president of the company went through the plating room one day, and, while chatting with him, Mr. Shepard suggested that he would like to obtain for use on his potash cleaning tank a controller, possibly one which had been returned and reconditioned. After listening to Mr. Shepard’s arguments as to why controllers should be used on the various tanks, Mr. Bristol, the president of the company, told him that he had permission to put controllers on each tank in the plating room where he felt the controller would be of assistance.
So in a very short time controllers were installed on the potash tank, the pickle tank, all the rinse tanks and the copper plating and nickel plating tanks.

”It so happens that the steam main supplying the plating room runs through the japan room next door, one branch line takes care of the japan ovens and another branch line takes care of the plating room. The japan ovens are filled up during the day and baked during the night. When the watchman shuts off the steam to the japanning ovens, he turns on the steam in the other line to the plating room. When the workmen reach the plating room, every tank is at the proper temperature, thanks to the automatic temperature controllers, and absolutely no time is lost waiting for the solutions to reach their proper working temperatures. From the date of the installation there have been no solutions wasted because tanks have boiled over; instead, the solutions have always been maintained at the proper temperature, which means that the minimum amount of steam or power has been expended and the plating department has been able to handle a greater volume of work more uniformly and economically.

”Again we repeat that temperature controllers can conserve time, labor, material and power. It has been proved over and over again and although temperature controllers have not been used to such an extent in the plating room as in some industries, their use in the plating room is on the increase, which shows that the platers do realize their value and are beginning to depend upon controllers more and more to help them produce their products uniformly and economically.”

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