224 



THE INDIA RUBBER WORLD 



[February 1, 1916. 



What the Rubber Chemists Are Doing. 



PRESIDENT RICHARD C. MACLAURIN, of the Massa- 

 chusetts Institute of Technolog)-, in a recent address be- 

 fore the New York Section of the American Chemical So- 

 ciety, said : 



We are hurt here (in America") by the prevalence of the 

 spirit of trade secrecy. Of course, we recognize a large part 

 of what is thought of as "secret" is really widely known, and 

 there is much knowledge of value that could be disclosed 

 without any detriment whatever to the revealer. 



There is still with us too much of the spirit of the pre- 

 scientitic days and too much reliance on "rule of thumb." Old- 

 fashioned superintendents are still constantly employed who have 

 no knowledge of science and little faith in it. Practical men must 

 not be so scornful of what is obvious to men of science. 



When the war is over the conditions of competition will be 

 peculiarly severe, but the war should have given our chemical in- 

 dustries a new start and a fresh impetus, and if our range of 

 vision is long and our enterprise does not fail, the future of 

 chemical industry in this country should be bright indeed. 



ARTTFICI.AL Rl-P,BER FROM VODKA. 



Since the outbreak of the war, when the sale of vodka in Rus- 

 sia was prohibited, the Imperial Minister of Finance has instituted 

 researches to adapt the national intoxicant to technical purposes 

 which would permit the government to profitably dispose of the 

 260,000,000 or more gallons now in stock. In a recent issue of the 

 Petrograd "Nowje Wremja," a chemist nained Ostromyslensky is 

 credited with having discovered a process for making artificial 

 rubber from vodka so successfully that the government has de- 

 cided to erect a large plant for manufacturing "vodka rubber." 



In this connection it should be noted that United States patent 

 1.161,904, recently granted to David Spence and Alexander P. 

 Clark, assignors to The B. F. Goodrich Co., covers a process for 

 obtaining rubber-like substances from alcohols. [The Indi.^ 

 Rubber Wobld, January, 1916, page 169.] 



METHODS OF ANALYSIS. 



Determinatiox of Sulphur ix Rubber. — The following 

 method was devised by Dr. Ludwig Rosenstein : 



Weigh out exactly 0.5 grm. of the finely ground sample in a 

 300 cc. Erlenmeyer flask. Add IS cc. of a saturated solution of 

 arsenic acid, 10 cc. of fuming nitric acid and 3 cc. of saturated 

 bromine water. Cover with a watch glass and boil until the 

 sample is completely oxidized and a clear solution is obtained, 

 adding more fuming nitric if necessary to complete the oxidation. 

 Evaporate to syrupy condition, then add a few crystals of potas- 

 sium chlorate to insure complete oxidation and to expel oxides 

 of nitrogen. Continue the evaporation almost to dryness to insure 

 complete expulsion of oxides of nitrogen. Cool and take up with 

 50 cc. of 10 per cent hydrochloric acid, heat on steam bath until 

 solution is complete, fitter to free from any insoluble matter and 

 dilute the filtrate to about 300 cc. From this solution the sulphur, 

 which has been converted to sulphate, may be precipitated with 

 barium chloride. Filter and weigh, observing the usual procedure 

 and take special precaution that precipitate be filtered from the 

 hot solution and washed with hot water to remove any lead salts. 



The function of the arsenic acid is to raise the boiling point 

 of the solution during the oxidation, thus making it more com- 

 plete and rapid. It may be prepared by adding C. P. arsenic 

 oxide to boiling water until boiling point of the solution is 140 

 degrees C. 



This method has been found rapid and accurate to within less 

 than 0.1 per cent on rubber mixings, both cured and uncured 

 containing known amount of sulphur, with and without various 

 compounding ingredients. 



ICl.ECTROLVTIC MeTHOU FOR LeaD AND ZiNC IN RUBBER CoM- 



I'OUNDS. — The fullowing method, by Elmer D. Donaldson, is of 

 interest. The portion relating to the deposition of zinc on plati- 

 num direct is adapted from a recently published method by W. S. 

 Kimley used for determining zinc in bronze and brass. 



Donaldson's method consists of digestion of the ash in nitric 

 acid and precipitation of lead as peroxide (PbO,), followed by 

 evaporation and precipitation of zinc as metal, both on platinum. 

 The electrolytic apparatus was equipped with a rotating electrode 

 and pole-reversing switch. The larger electrodes were of plati- 

 num gauze V/i inches wide by 2 inches high, sand blasted, and 

 the rotating gauze Vz inch wide by, 2 inches high. The apparatus 

 was connected to a 110 volt direct current generator and lamp 

 resistance. 



Lead — Weigh 1 gram rubber, wrap in a 7 centimeter ashless 

 paper and incinerate in a 20 to 30 cc. porcelain crucible. Brush 

 the ash into a 200 cc. electrolytic beaker, add 25 cc. concentrated 

 nitric acid, and digest on hot plate for 15 minutes. Boil to expel 

 nitrous fumes and dilute to about 125 cc, having solution at 158 

 degrees to 176 degrees F. Electrolyze with rotating cathode, using 

 direct current of two to three amperes. The lead will appear 

 on the large gauze anode as peroxide, black when in large 

 amounts, bronze colored w^hen in small amounts. Electrolyze 30 

 minutes and wash anode thoroughly with water to remove me- 

 chanical impurities, then with alcohol and ether. Dry for 30 

 minutes at 338 degrees F. Weigh as peroxide of lead (PbO,; 

 and for convenience calculate to litharge (PbO), using the factor 

 0.9.33. No metals present in rubber mixings will interfere with 

 this determination. 



Zinc — Wash the solution and the insoluble matter from the 

 electrolytic beaker, from which the lead has been removed, into a 

 litre beaker. Add 5 cc. concentrated sulphuric acid, evaporate 

 dry. and drive off most of the sulphuric acid. This is done to 

 insure complete removal of nitric acid, which would interfere 

 with the electro deposition of zinc. After evaporation, cool and 

 digest residue, which usually contains considerable insoluble, with 

 50-75 cc. water. The zinc is now present as zinc sulphate and is 

 readily soluble. Filter and wash. If the zinc oxide content is 

 known to be low use entire filtrate, but if 20 per cent or over, 

 catch filtrate in 200 cc. volumetric flask. ^lake up to mark and 

 take 50 cc. 



Wash this portion of solution representing 0.25 grams of rubber 

 sample into a 200 cc. electrolytic beaker. Add considerable excess 

 of saturated solution of sodium hydroxide over that necessary to 

 redissolve the zinc hydroxide. Electrolyze at ordinary tempera- 

 ture at 2 to 2.5 amperes, rotating the anode for 20 minutes. Re- 

 move and wash with water, alcohol and ether. Dry at 212 de- 

 grees F. for a few minutes, coo! and weigh. 



Zinc is deposited on the cathode and is weighed as metal. The 

 weight of zinc is calculated to zinc oxide. Aluminum will not 

 interfere even if the solution is gelatinous from the precipitated 

 aluminum hydroxide. In event that iron is present, filter ofT 

 the iron hydroxide after adding just enough sodium hydroxide 

 solution to insure solution of the zinc hydroxide. Then add 

 further sodium hydroxide solution to this filtrate. Lead peroxide 

 and zinc can be dissolved from the platinum gauze by concen- 

 trated nitric acid saturated with tartaric acid. 



Preparation of Rubber Samples for Analysis. — Soft vulcan- 

 ized rubber of high grade requires to be finely divided for suc- 

 cessful analysis by extraction methods. It has recently been 

 suggested by John H. Link to use for this purpose an "Enter- 

 prise" food masticator. No. 1 size. Repeated passage through 

 the machine will, in a few minutes, cut an ounce of soft cured 

 rubber sufficiently fine to pass through a 20-mesh sieve. 



