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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
without attaining a strength greater t h a n 63 t o 64' BC. and t h e gases will pass out of t h e tower entirely too hot, going as high as 350 t o 360" F.; also t h e suction of t h e flue leaving t h e tower will drop t o almost nothing, while t h e temperature of t h e gas entering t h e tower will decrease from 2 0 0 t o 300' F. The above-described conditions were t h e ones t h a t were corrected by introducing broken quartz through t h e lute a t t h e t o p of t h e tower. DIFFICULTY
WITH
AN
OPEN
BRICK
LINING B E T W E E N
T H E PACKING A N D LEAD
T h e writer had a very peculiar experience on one occasion. T h e tower showed all symptoms of being too open. It was s h u t down and t h e t o p removed b u t t h e packing appeared t o be in perfect condition. However, as i t was quite evident t h a t t h e gas was passing too freely through t h e tower and as we had been unable t o get any 66" acid from this unit for several days previous, i t was decided t o remove t h e packing, not disturbing, however, t h e 18-in. brick lining between t h e packing a n d lead. After t h e packing h a d been removed and t h e tower repacked, t h e plant was started up, b u t with no better results t h a n before. It is needless t o say t h a t t h e writer was very much concerned about t h e matter, as t h e tower would not produce 66" acid a n d yet there was nothing apparently wrong with t h e packing. However, t h e t o p was removed again a n d a very careful examination was made t o determine, if possible, how t h e gas was slipping through t h e tower with so little resistance. It was observed t h a t t h e brick wall between packing a n d lead was very open, there being spaces of from to in. between t h e bricks a n d as t h e bricks had been laid dry. with t h e exception of about 3 in. on t h e edge of t h e wall, it was decided t h a t t h e heat was evidently coming u p through t h e wall a n d not through t h e packing, as i t should. T h e wall was taken down t o t h e level of t h e packing (about 5 ft. from t o p of tower) a n d acid-proof cement, consisting of silicate of soda a n d silax, was poured down through crevices in t h e wall a n d a small amount of i t appeared under t h e arches, proving t h a t t h e theory of t h e heat going u p through t h e wall was a correct one. The wall was then laid from t h e t o p of t h e packing up in mortar made from silicate of soda a n d silax. This mortar was used very liberally, making t h e bricks tight with it, just as would be done in building a n ordinary brick wall. When this work had been finished t h e t o p was replaced a n d plant started u p ; i t worked beautifully, even better t h a n i t h a d ever worked before. LOSSES OF ACID I N THE COKCENTRATOR AKD REGULATION OF DRAUGHT
I n regard t o losses of acid in t h e concentrator under normal conditions, when t h e tower was being fed with 60,000 lbs. of 60' acid in 24 hrs., t h e losses would amount t o from 2 , 0 0 0 t o 4,000 lbs. of 60' BC. acid per d a y of 24 hrs. and there would be recovered as 66" B&. acid about 39,000 lbs., equivalent t o 46,792 lbs. of 60" B4, acid and t h e balance, or 9,208 lbs., would be recovered in t h e distillates from scrubbers. This scrubber acid runs about 46' BC. It is
Vol. 9, No. 4
pumped over t o t h e sulfuric acid plant and sent down t h e Glover tower, where i t is brought up t o 60" BC. along with t h e other acid passing over a Glover tower, after which i t is returned t o t h e concentrating plant again. T h e losses varied greatly, according t o t h e amount of draught t h a t was used. When a very strong draught was being used i t was found t h a t t h e loss of H2S04 was very much greater t h a n was sustained when only a moderate draught was being used on plant. W e , therefore, tried t o get t h e happy medium of using just enough draught t o take t h e distillate from t h e top of t h e tower and at same time not t o have too great a loss at t h e exit stack. I n connection with t h e above, i t was found t h a t when using Lunge's method, namely, I O cc. of iV/ro caustic soda solution a n d aspirating gas through t h e same t h a t t h e loss of SOs would r u n from 0 . 2 5 t o 0 . j per cent. This test was made twice daily on each plant and was depended upon t o a certain extent t o determine t h e amount of draught which should be used, but as t h e tower very rapidly became choked, necessitating a constant increase of draught, t h e testing of t h e gases was of very small benefit in regulating t h e plant. However, if i t were possible t o get a tower packing t h a t would not disintegrate, so t h a t t h e opening would s t a y uniform, t h e testing of t h e exit gases could be used t o a great advantage as a method of control. SOUTHERN FERTILIZER A N D CHEMICAL COMPANY SAVANNAH, GEORGIA
PRINTING PLATES FROM PHENOL RESIN COMPOUNDS By I,. V. REDMAN, A. J, WEITH,F. P. BROCK Received January 26, 1917
T h e growth of syndicate work in illustrated advertising, comic supplement a n d "filler" for our 30,000 American Newspapers, has created a need for a material which will lend itself t o t h e rapid production of printing plates in manifold. T h e plate requires t o be produced rapidly a n d inexpensively a n d must be of such quality as will print clearly on t h e cheap sheet used by daily papers. Such a plate is in no way intended t o take t h e place of copper, zinc, stone or wood cuts where there is needed only one cut or a t most a very few cuts of any one subject, such as in t h e printing of magazines, books, and catalogs. T h e new plate is designed t o fill t h e need of thousands of daily papers which require t h e same news t o print at t h e same time, either advertising, comic supplement, news of general interest t o t h e country or "filler" for dailies or weeklies. Printing plates for this work have been made from celluloid compounds a n d shellac by pressing t h e celluloid or shellac plastic into t h e original papier m$chC mat which had previously received an impression from t h e zinc etching. T h e celluloid plate is used extensively. T h e shellac plate does not seem t o h a v e made its way t o a commercial success. T h e shellac a n d celluloid plates will not stand t h e heat, pressure a n d moisture required for making t h e papier miich6 mat for stereotype machines. Also t h e "dots" making u p t h e screen in half-tones of celluloid are not full
Apr..
'I;
1'111:' J O U R N A L
#F I N D U S T R I A L I ~ N D~ J I V G I L V ~ M R I A ' L'IlE.MIS2'KY G
aiid perfect. The shellac plate is brittle a n d requires careful handling. is possible t h a t a hard ri,bher he highly The time vulcanization, high cost of materials anti t h e fact tiiat hard at 7oo c. &tort under pressure are the cliief flictors against such n plate. The [jualities possessed by phenol resin molding compounds make these materials highly valuable for printing plates. T h e heat resistance, strength iii thin sheets, resistance t o waicr, and the accuracy and speed with which they may be molded make them a n excellent material for t h e proiiuctioii of printing plates in multiple. These plates may Le used for direct printing on flat bed presses or may serve as a c n t from which to make t h e papier m%ch4 mats for stereotypes. Practical difficulties have presented themselves in obtaining a satisfactory mold for use in making manifold plates from phenol molding compounds. If t h e molds-he made from a high-grade steel and case-hardened, t h e expense is prohibitive; if the original zinc etching be used, a negative figure or picture is produced on t h e molded phenol sheet; a n d if a mold be made of the zinc or lead etchings, t h e pressure required for forming t h e phenol resin into shape destroys t h e sharpness of the zinc or lead c u t after a few operations. A satisfactory mold in every way can be made from the phenol molding compounds. The method of producing t h e mold in which is made t h e printing plate in manifold is as follows: A sheet of t h e plastic phenol molding compound is placed on a hot plate or steam table t h e same as in shcllac molding a n d is kept there until t h e sheet has licated through and become soft and pliable. The original zinc etching is then placed on t o p of t h e warm plastic sheet and both are placed in a hot press. Any source of heat, gas, steam or electricity, will do for t h e hot press. I n this case steam is t h e most satisfactory a n d electricity t h e least desirable. The pressure is raised gradually t o about 2000 Ibs. per sq. in., and t h e compound is allowed t o harden for a few minutes. Controlling bars prevent t h e press heads from coming too close together. a n d insure a n accurate thickness for t h e mold and later also for t h e printing plate. Open on every side, t h e plastic compound is allowed t o flow out around t h e edges. The mold is formed this way t o a pre-determined thickness, generally to in. The temperature a t which the operation is carried o n varies from 285 t o 400' F., depending upon t h e quality of t h e material used, and t h e time during which t h e material is to be left in t h e Dress. Loneer time a n d lower temperature give a tougher product t h a n do the higher temperatures a n d shorter time. In this respect, t h e hardening of all phenol resins bears a very close similarity to t h e vulcanization of rubber. The plastic sheet as soon a s i t has hardened is removed hot from t h e press, and t h e zinc or lead etching IS taken off. The plastic sheet is now hard a n d has on its face t h e negative ol the original zinc etching,
389
and in practice is known as t h e mold. On this negative cast or mold, warm fresh plastic sheet is laid, placed carefully in t h e press and subjected t o pressure for a few minutes. As Soon as t h e fresh sheet has hardened it is rcmovcd from t h c mold. This time t h e positive printing plate is produced, i t being t h e reverse of t h e negative mold. This second molding operation re-
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Fig. I Printing P l a t e Molded a l r e a d y blocked
Combination of Half-tone, Line & P r i n t
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Fig. Boiler P l a t e Ready f o r Mounting Showing D i f f e r e n t Types Reproduced on One C u t -+
I
quires about ten minutes for a complete cycle of operations, a n d may be reproduced many thousands of times with no appreciable deterioration t o t h e original mold made from t h e phenol plastic. Since t h e average single column cut is about two inches by three inches, and a satisfactory commercial press is eighteen inches by eighteen inches, this allows three hundred plates per hour to be made in a single two-platen press.
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T H E JO.URNAL OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
AS the plastic sheet and mold would naturally weld together in the hot press, various methods are used t o prevent the plate sticking t o the negative mold or cast. A layer of oiled paper, thin metal, talc dust, etc., between t h e mold and cast has proven satisfactory but care must be taken when using paper or foil t o see t h a t it is not torn or trouble may result. The use of t h e foil or paper produces a rounded point'to t h e half-tone screen and produces a more desirable printing plate t h a n t h e original zinc etching which generally has a protruding crown or shoulder thereby allowing ink t o collect behind t h e point, soon blurring t h e plate. The smooth rounded point produced on t h e phenol plastic by the use of the intermediate paper or metal foil makes a plate which does not gum up and blur with t h e printing ink. Half-tones have been produced from I 50-mesh screen and 1 5 0 screen is t h e highest used in ordinary halftone work. The ordinary newspaper cut is produced from screen not exceeding IOO mesh, as t h e larger dot is required for printing on coarse cheap paper. Any form of line work can be reproduced with accuracy and is in general an easier proposition t o handle t h a n t h e half-tone. Mounted plates may be molded directly upon t h e block of wood and come from the press blocked and ready for flat bed printing. I n this form the cut cannot be unblocked. The plates are also produced in thin form (1/16 inch thick) and are afterwards in another operation blocked by tacking or gluing like t h e regular zinc cuts. Plates blocked or mounted on wooden blocks by tacking may be readily unblocked. The weight of t h e molded plate is one-sixth t h e weight of t h e corresponding zinc, etchings, and contributes a saving in shipping costs equal t o t h e original cost of t h e plate. One square inch of plate weighs l / p oz. Ready for shipping 35 sq. in. weighs 4 oz. I t should be borne in mind in this case t h a t in extensive advertising t h e cost of mailing or expressing t h e zinc cuts is often equal t o t h e original cost of the etching. REDMANOL CHEMICAL PRODUCTS COMPANY 636 w. 22ND STREET CHICAGO
THE SETTING OF LITHARGE-GLYCERINE CEMENT' B y H. E. MERWIN Received December 26, 1916
A little litharge which had passed a zoo-mesh screen was spread in a large excess of glycerine on a microscope slide under a cover-glass. After a n hour indications of t h e crystallization of another substance around t h e surfaces of t h e litharge grains could be seen; after three hours t h e new substance was very apparent; and after 2 4 hrs. t h e original grains of litharge were replaced or firmly bound together by interlocking crystalline aggregates of t h e new substance. These aggregates consisted of radiating fibers. Grains in a similar slide held a t 80" C. for an hour were firmly cemented. The new crystals had similar optical properties in both cases. This cement is very important and not fully appreciated, e. g., it is used in very large quantities in lining the digesters in the manufacture of sulfite~pulp.-EDIToR's NOTE. 1
Vol. 9, No. 4
Glycerine, pure or diluted with j t o I O per cent of alcohol or water, heated t o boiling and agitated with litharge, gave similar crystals which were much less closely aggregated. Agitation prevented t o a large extent t h e covering of t h e litharge grains by t h e new crystals. I n the best sample of material thus prepared-afterwards used for analysis-about I O per cent by volume of unattacked litharge and g o per cent new crystals were estimated microscopically. Analysis showed 70.8 per cent of P b , which corresponds t o 5 per cent residual PbO, and g ; per cent of t h e compound' C3H602.Pb0,representing t h e new crystals. The crystals are apparently orthorhombic. The refractive indices are, a = 1.75, /3 = 1.80, y = 1.84, with y parallel t o t h e length. The crystals had been slightly attacked by t h e alcohol used in washing them. After standing with glycerine for several days a t ordinary temperatures t h e centers of the larger grains of litharge t h a t had passed a zoo-mesh sieve were still unattacked. Probably coarser grains would remain indefinitely. GEOPHYSICAL LABORATORY CARNEGIE INSTITUTION OF WASHIIGTON D C. WASHINGTON,
THE USE OF A CONDENSER TO PREVENT ARCING IN BOMB CALORIMETERS B y FREDF. FLANDERS Received January 16, 1917
Commercial lighting current of I I O volts is quite commonly used for igniting the charge in bomb calorimeters. A typical arrangement is t o connect two 32C. P. lamps in series with t h e fuse wire. Objections have been raised t o the use of current of such high voltage on account of the uncertain amount of heat developed b y t h e arc formed a t t h e instant the fuse wire burns out.2 The arc may be entirely obviated by t h e use of a 2 mf. condenser. This is connected across t h e leads running t o the fuse wire a n d as close t o t h e latter a s possible. When protected in this manner t h e IIOvolt current produces scarcely a visible spark when t h e current is broken. The use of t h e condenser might also prove advantageous where a storage battery or other source of low voltage current is used, for even with voltages as low as I O or 1 2 volts there is still a n appreciable arc when t h e current is broken. Condensers satisfactory for t h e above use may be had of almost any electrical supply house, particularly those dealing in wireless apparatus. They are listed as flat telephone condensers, should be of about z mf. capacity a n d tested for 500 volts. A very neat one, z X 4 X s/4 inches, was supplied by the Clapp-Eastham Co., of. Cambridge, Mass., for ninety cents. CHEMICAL LABORATORY ON MENTAL DISEASES MASS.COMMISSION 74 FENWOODROAD, BOSTON 1
This compound was prepared by T. Morawski 1.7. prakt. Chcm..
J., 256, 2131 in his original studies of this cement. 2 U. S. Bureau of Standards, Circular 11, p. 7, issue of May 15, 1911. THIS JOURNAL, 9 (1917). 106. Under (6). Firing current.
22 (1880). 401, and Dingier's p d y f e c h .
