TSE INDIA" RUBBER WORLD 



[Jui-Y 1, 1916. 



chloroisopentane. This residue may be filtered through 

 glass wool and the filtrate weighed. The fraction boiling at 

 194 to 266 F. is subjected to" carWiir fractio'ftar distillation, as 

 it contains 1.3-dichloroisopentane, sometimes in considerable 

 quantity. The fractionation is carried , out three times in 

 each case up to 288 degrees F. 



ANALYSIS OF LITHOPONE. 



THE tentative methods of the American Society for- Testing 

 Materials for the analysis of lithopone are as follows: 



Insoluble M.\tter. Take 1 gram of the sample in a 200 

 cc. beaker, add 10 cc. of concentrated hydrochloric acid and 

 mix;. Add in small portions about 1 gram of potassium chlorate; 

 then heat on steam bath until about half of the liquid is evap- 

 orated. Dilute with water, add 5 cc. of dilute sulphuric acid 

 (1 pdrt of acid to 10 of water); boil, settle, filter, wash, ignite, 

 cool and weigh the insoluble matter, which should be only barium 

 sulphate. 



ToT.^L Zinc. The filtrate from the insoluble matter is made 

 alkaline with caustic soda, acid with hydrochloric acid, add 3 cc. 

 of concentrated hydrochloric acid, dilute to about 250 cc. with 

 water, heat nearly to boiling, and titrate with potassium ferro- 

 cyanide solution and calculate to zinc. 



Zinc Oxide. Treat a 4 gram sample of lithopone for 4 hours 

 with 200 cc. of 1 per cent acetic acid at ordinary temperature, 

 stirring occasionally. Filter by suction on a double filter paper 

 and wash with cold water ; add to the clear filtrate 13 cc. of 

 concentrated ammonia water, neutralize with hydrochloric acid, 

 and then add 3 cc. of concentrated hydrochloric acid in excess; 

 heat to boiling and titrate with potassium ferrocyanide, using 

 uranium acetate solution as an outside indicator. Calculate to 

 zinc o.xide. Calculate this result to zinc, deduct from total 

 zinc, and calculate difference to zinc sulphide. Zinc carbonate 

 or zinc sulphate is included in the zinc oxide. 



Zinc Sui.phiiie. Place OS gram of pigment in evolution flask' 

 with about 10 grams of mossy zinc, add 5 cc. of water; insert 

 the stopper carrying a separatory funnel and an exit tube. Run 

 in SO cc. of concentrated hydrochloric acid from the funnel, having 

 previously connected the e.xit tube to two absorption flasks in 

 series; first flask contains 100 cc. of alkaline lead nitrate solu- 

 tion, second flask 50 cc. of same as a safety device. After all 

 of the acid has run into the evolution flask heat slowly, finally 

 boiling until the first appearance of steam in the first absorption 

 flask ; disconnect, let the lead sulphide settle, filter, wash with 

 cold Water, then with hot water till neutral to litmus paper and 

 washings give no test for lead. The lead sulphide precipitate is 

 dissolved in hot, dilute nitric acid, evaporated to fumes with sul- 

 phuric acid, and finally weighed as lead sulphate. Calculate to 

 zinc sulphide. 



The alkaline lead solution is made as follows: Into 100 cc. 

 of 'potassium hydrate solution (S6 grams in 140 cc. of water) 

 pour a saturated solution of lead nitrate (250 grams in 500 cc. 

 of' water) until the precipitate ceases to redissolve, stirring 

 constantly while mixitig. Abouf 3 volumes of the lead solu- 

 tion will be required for one of the alkali. 



Instead of absorbing the evolved sulphuretted hydrogen in 

 alkaline lead nitrate solution, a solution of 8 grams of cadmium 

 chloride in 250 cc. of water and 150 cc. of ammonia water 

 (sp. gr. ■ 0.90) may be used. The cadmium' sulphide precip- 

 itated, may be filtered on' a weighed Gooch, washed with water 

 containing a little ammonia, dried at 212 degrees F., and weighed. 

 Calculate to zinc sulphide. It is better to filter the cadmium 

 sulphide on a small filter and wash as above, then place filter 

 and ' precipitate in a beaker and dissolve in hydrochloric acid 

 and potassium chlorate (keeping at room temperature at first) ; 

 filter out any paper pulp or insoluble matter; make filtrate 

 alkaline with ammonia water, then just acid with hydrochloric 

 acid, heat to boiling, and precipitate with barium chloride in the 



usual manner. Filter, wash, ignite and weigh as barium sul- 

 phate. Calculate to zinc sulphide. 



For very rapid worklhe contents of the absorption flask, after 

 all sulphuretted hydrogen has been absorbed, may be washed 

 into a vessel with cold water, and diluted to about one liter, 

 acidified with concentrated hydrochloric acid, and titrated with 

 standard iodine . solution, using starch indicator. (The pre- 

 cipitate should be completely dissolved.) The iodine solution 

 is prepared by dissolving about 12.7 grams of pure resublimed 

 iodine and 18 grams of potassium iodide in a little water, and 

 then diluting to one liter. 



tests' ON LITHOPONE.* 



Color. The color of tlie dry pigment should be compared with' 

 a standard sample of pure dry zinc oxide and a standard sample of 

 lithopone that has been kept in a colored glass jar protected 

 from light. Portions of these samples should then be ground in 

 light colored linseed oil and again compared for whiteness. 



Op.\city. The relative opacity or "dense" character of the 

 samples may be determined by making small batches of paste 

 paint with mortar and pestle. To 25 grams of lithopone add 2 

 grams of 98 per cent i-ed oxide of iron. Use about 10 grams 

 of raw linseed oil (pale) for grinding. Brush out a sample of 

 the paint upon a strip of glass in comparison with others pre- 

 pared in the same manner. The most "dense" grade of lithopone 

 will give the lightest effect. 



TESTING RUBBER INSULATION. 



In testing rubber insulation according to the 'Underwriters' 

 Specifications, Aaron Arthur Ladon, Chicago, Illinois, has found 

 that samples taken from the same coil showed marked variation 

 in strength and elongation. The wire had been in stock some 

 time and the tests were carried out with the idea of putting it in 

 with the new stock, provided the insulation had not deteriorated. 



Samples 5 inches long were taken from each coil. They were 

 rolled between two blocks of wood to loosen the insulation. The 

 rubber could then be slipped off the wire. The- insulating mate- 

 rial was then tested for elongation, stretch and tensile strength. 



The results varied as much as JOO per cent, and in only six ■ 

 coils out of 52 did the samples check. 



The trouble did not lie in non-uniformity or deterioration of 

 the rubber cumii.aiml, a^ \\a^ In^t ^u|lpnsell. The method of 

 separating the wire iLmi ilu iiiMilati..n was at fault. Xo matter 

 how carefully the saiiipK- hcic r^.lKcl between the two blocks, 

 the insulation could not be removed intact. In places it- would- 

 stick to the wire. ''^ '"-..-•■- • :: j ■■„ 



A new method was therefore devised for removing the insula- 

 tion. The wire was tinned copper. Tin amalgamates with mer- 

 cury very easily and forms a very slippery surface on the copper. 

 The mercury has no effect oh the rubber compound. About 54 

 inch of insulation was cut off of each end of the samples and 

 the stripped wire scraped to remove dirt and grease. The ends 

 of the samples were then immersed in mercury. After a period 

 of time, varying from 4 to 24 hours, the insulation could be 

 slipped off the wire with almost no effort. 



This method is being used by one of the largest electrical 

 manufacturers in the country. Besides the accuracy and uni- 

 formity of results accompanying the application of this property 

 of mercury, the cost of the testing has been reduced by over one- 

 third. 



A NEW SOURCE OF ANTIMONY. 



Alaska, during 1915, shipped to San Francisco about 800 tons 

 of antimony, chiefly from the region about Fairbanks. Four 

 deposits are being worked on a small scale. The mineral is 

 found in pockets and contains SO to 58 per cent of metallic anti- 

 mony. This discovery is not remarkable, since antimony is fre- 

 quently found in abundance in gold bearing strata. 



Gardner. Director, Scientific Sectioi, 



Edu 



tional riur 



Mannfactu 



