638 



THE INDIA RUBBER WORLD 



Jink 1, 1921 



side of the package is opened, and finally bands the five sticks 

 together and seals the package with paste. The individual sticks, 

 inside bands and outside bands are fed from magazines and the 



Americai: l - 



Fig. 14. Packaging Dep.\rtment 



Toil or waxed paper for the first wrapping is fed from a roll and 

 <:ut to proper length. The output of the machine is 100 boxes of 

 20 packages per hour. 



ANTIMONY SULPHURET, ITS MANUFACTURE AND 



USE' 

 By D. A. Shirk' 



IN the rubber industry, "antimony sulphuret" is the trade name 

 applied to precipitated sulphides of antimony containing vari- 

 ous percentages of free sulphur and adulterants. The sulphides 

 are generally present as pentasulphide or oxysulphide. With cer- 

 tain exceptions, manufacturers use the words "golden" and "crim- 

 son" to indicate pentasulphide and oxysulphide, respectively, and 

 the word "golden-crimson" when both are present. 



GOLDEN ANTIMONY 



Golden antimony is obtained from the reaction between either 

 .calcium sulphantimonate, CaaCSbSj), or sodium sulphantimonate, 

 I^'asSbSi and either sulphuric, sulphurous or hydrochloric acid. 

 It is evident that when sulphuric acid is employed to precipitate 

 from the calcium solution that calcium sulphate is also precipi- 

 tated. This calcium sulphate being quite insoluble remains in the 

 .final product and dries to CaS0..2H,0. The free acid is generally 

 washed out by decantation or filtering, although it is sometimes 

 neutralized with an excess of calcium carbonate or calcium hy- 

 ■droxide. Irregularities in the preparation of the salt solutions, 

 concentrations, temperatures, washing, drying and grinding will 

 result in products which, although they may be superficially sim- 

 ilar will give many different results under vulcanization. 



CRIMSON ANTIMONY 



Crimson antimony is commercially produced by the reaction 

 between sodium or calcium thiosulphate and a solution of an- 

 timony trichloride in hydrochloric acid, or a suspension of an- 

 timony oxychloride in an acid solution. The calcium salt is not 

 as stable as the sodium salt and where it is used there is often 

 •present in the finished product certain quantities of calcium sul- 

 phite. This product is always tested for acid and should be 

 'tested for chlorides as well. It is well known that good qualities 

 of both crimson and golden antimony will sometimes after long 

 Standing give a faintly acid reaction due to the formation of a 



iTlic Rubber Ace. New York, Mav 10, 1921. 



*The Rare Metal Products Co., Belleville, New Jersey. 



very small amount of sulphur dioxide. This should not be con- 

 fused with the presence of traces of hydrochloric acid or an- 

 timony chloride, the responsibility for which must be borne by 

 the producer. 



COLOR OF ANTIMONY 



The color of antimony, or rather its ability to retain its color 

 at elevated temperatures, is of important consideration. Contrary 

 to the popular belief a rclialile grade of golden antimony, or pen- 

 tasulphide, does not, under vulcanization, decompose to Sb^Sa and 

 sulphur. The physical stability of color is an indication of the 

 chemical stability of the pentasulphide. When golden antimony 

 is subjected to elevated temperatures it does not yield any free 

 .'^iilphur until its color changes. As the color changes to brown 

 certain amounts of free sulphur appear and finally when the color 

 becomes black the amount of free sulphur yielded is about equiv- 

 alent to the amount calculated upon the theoretical decomposition 

 of the pentasulphide to the trisulphide. It becomes evident, there- 

 fore, that to use a golden that just turned brown under cure 

 would result in a situation where the total amount of free sul- 

 Iihur acting would be very indefinite. 



ADVANTAGES IN RUBBER GOODS 



Antimony sulphuret of proper grade and properly used has 

 three distinct advantages. First, it is an accelerator. Antimony 

 sulphuret in a compound will enable the maximum cure to be 

 obtained at a given temperature and time with the use of less 

 free sulphur. This presents the great advantage of reducing the 

 amount of uncombined free sulphur in the vulcanized product. 

 This in itself gives one explanation of the second advantage, 

 namely, good aging. The superior aging quality of a good red 

 tube is quite generally recognized. 



A third advantage is the increased sales value of a bright clean 

 orange or red stock over a blooming grey stock. Some manu- 

 facturers use antimony because the free sulphur it carries is 

 generally all precipitated and hence in a much finer state of 

 division than the ordinary flour sulphur. Others stress the fact 

 that with antimony they obtain a stock of much softer "feel" 

 than with any other compounding ingredient. 



SOURCES OF SUPPLY 



Prior to September, 1914, there was in the United States only 

 one manufacturer of antimony sulphuret in quantity. England 

 and France furnished the major part of the antimony used in 

 this country, although just at that time Germany was beginning 

 to make serious inroads into the business of their other European 

 competitors. When the war shut ofT the European supply Ameri- 

 can iTianufacturers met the situation with products which today 

 represent the very best that can be found in any market. 



POINTS ON QUALITY 



There arc not many differences between a pure golden or crim- 

 son antimony aside from color and price. The crimson is con- 

 siderably more expensive but imparts to the stock a deep red 

 color that the pentasulphide will not give. On the other hand, 

 many prefer the golden shade when it is clean and bright. The 

 chemist should be particular that the antimony retains the bril- 

 liancy of its color under his particular conditions of vulcanization, 

 for the reasons given above. The best texture cannot be obtained 

 where there is any large quantity of calcium sulphate. This is 

 chiefly due to the large particle size of this material. Every 

 rubber chemist wishing to be sure of his ground on antimony 

 should make a careful study of particle size and agglomeration. 

 Everytliing else being the same, the percentage of antimony sul- 

 phide present should determine the price. Most of the uncer- 

 tainty and distress in the use of antimony in rubber work will 

 permanently disappear when the trade accepts as a standard an 

 acid- free, pure, stable pentasulphide, of a specific state of division, 

 carrying a specified percentage of free sulphur. 



