May 1, 1916.] 



THE INDIA RUBBER WORLD 



411 



l-RKE SuLPHiR. — Take acetone extract (rubber resins) in a fat 

 ilask, moisten with water and cautiously add 25 cc. fuming nitric 

 acid, cooling the flask in ice. Then gently warm and finally digest 

 on steam bath, using a funnel as cover. When action is com- 

 plete wash into a porcelain dish with a few cc. of fuming nitric 

 acid and evaporate off all the acid. Ail the sulphur is now con- 

 verted into sulphuric acid. Intimately mi.x the mass with 5 grams 

 of a mixture of 3 parts sodium carbonate and 2 parts potassium 

 nitrate ; moisten slightly with water and mix well. Cover with 

 a large dish and heat over a low flame till white. Cool and take 

 up with concentrated hydrochloric acid, evaporate to dryness 

 twice to precipitate silica and then finally dissolve in dilute hydro- 

 chloric acid, filter and precipitate as barium sulphate. Calculate 

 to sulphur. This gives the figure for free sulphur. 



Kl-bber Substitutes (O.nidized Oil. Etc.).— The residue from 

 the acetone extraction in the determination of rubber resins is di- 

 gested with 100 cc. approximately half normal alcoholic potash 

 for 4 hours at 140 to 158 degrees F. Pour off througli a filter and 

 digest residue twice with warm alcohol. Mix filtrate and alco- 

 holic washings and evaporate off nearly all the alcohol. Take up 

 the residue in a little cold wateri'transfer to a separating funnel, 

 acidify and remove the fatty acids with ether. Ether extract is 

 then taken to dryness and weighed. This gives fatty acids of 

 oxidized oils, and is taken as the percentage of rubber substitutes. 

 V'ULC.\NIZED Rubber.— This is obtained by subtracting the sum 

 of the other determinations from 100. 



Total Sulphur.— The method is the same as that described 

 under free sulphur only one uses the original rasped rubber. The 

 difference between total and free sulphur gives combined sulphur, 

 but as this is included in vulcanized rubber, it is seldom sepa- 

 ratelv expressed. 



FREE SULPHUR IN RUBBER INSULATION. 



The method for determining free sulphur in vulcanized rubber 

 insulation as developed by Emile Baldeschvvieler is as follows: 



The weight of the finely divided sample varies, but generally 2 

 grams is sufficient. It is extracted for 8 to 10 hours in a Soxhlet 

 apparatus with acetone at 131 degrees F. The apparatus is then dis- 

 connected, the excess of solvent evaporated, and the flask dried at 

 131 to 140 degrees F. Fuming nitric acid to the amount of 60 cc. 

 is then added to the residue in the flask, which is covered with a 

 watch glass, and contents boiled gently until most of the red 

 fumes have been expelled. 



The flask is then uncovered and a small pinch nf potassium 

 chlorate added to the boiling liquid. Continue the addition of 

 small amounts of potassium chlorate until the liquid is entirely 

 clear. When the greenish color has disappeared, remove the 

 flame and cool the flask in ice water. If properly conducted the 

 operations will yield a clear liquid with white flakes or a lump 

 of paraffin floating on top. 



This is separated by filtration and the filtrate, evaporated nearly 

 to dryness, is taken up with hydrochloric acid. The operation is 

 repeated several times to drive off the nitric acid. Dissolve the 

 residue in water, add Ice. dilute hydrochloric acid and filter into 

 a 500 cc. beaker. Make up to 400 cc. with water, heat to boiling 

 and add, drop by drop, a slight excess of a 10 per cent solution 

 of barium chloride. Filter and weigh as barium sulphate. 



DIRECT DETERMINATION OF RUBBER IN VULCANIZED RUBBER 

 G00D3. 



.\ combustion method for the direct determination of rubber 

 in vulcanized rubber goods has been developed by Robert W. 

 Belfit. It is simple, quick and accurate for high grade com- 

 pounds and preferable to those direct methods which depend 

 upon the formation of compounds, the exact formula; of wliicli 

 are not constant or controllable. 



The author states that his method is at present restricted to 

 positively high grade stocks, which do not contain lampblack, 

 reclaimed rubber or rubber substitutes. The method gives the 



percentage of rubber too high in the presence of ground leather, 

 egg all)umen or other organic compounds insoluble in acetone, 

 water and dilute hydrochloric acid. 



In detail the procedure is as follows : 



The sample is ground so that it will all pass through a 20-mesh 

 sieve while but 20 per cent passes through a 40-mesh sieve. 

 Then, 2 grams are extracted in a weighed tube for 5 hours with 

 acetone kept continually at the boiling point. The tube con- 

 taining the residue is inserted in an oven, kept at 212 degrees F.. 

 and a current of dry carbon dioxide is passed through the tube 

 in order to aid rapid drying and prevent oxidation. The dried 

 sample is weighed, and the percentage loss in weight calculated. 

 About one-half of this extracted sample is w^eighcd into a 

 250 cc. Erlenmeyer flask, and is cautiously boiled for 30 min- 

 utes with 150 cc. of hydrochloric acid (1 to 5 by volume). In 

 this process all carbonates are driven off. 



The liquid is decanted through an alundum crucible and the 

 residue is washed three times by decantation with water at 

 about 140 degrees F., then washed ten more times with warm 

 water. The residue is now placed in a tube and dried in a stream 

 of dry carbon dioxide at 212 degrees F. for two to four hours. 

 The tube is then removed and cooled in a desiccator. 



This dry residue is next transferred to a weighing tube, from 

 which 03-gram samples are weighed for combustion. The com- 

 bustion is carried out in approximately the same manner as for 

 any organic compound, except that no reduced copper spiral is 

 used, as the water and nitrogen oxides are absorbed in a con- 

 centrated solution of potassium dichromate in sulphuric acid. .\ 

 vessel of small volume is necessary for this solution, or otherwise 

 it is almost impossible to displace all of the carbon dioxide after 

 the sample has been completely burned. Beyond this tube is 

 placed a L'-tube containing zinc dust to absorb all possible acid 

 gases other than carbon dioxide. The potassium hydroxide ab- 

 sorption bulb is next and last in the train. The rubber substance 

 is burned in a stream of oxygen, and the potash bulb is always 

 weighed when full of oxygen. 



This method on pure, fine Para gum gave 96.16 and 96.57 per 

 cent. 



The value 0.96 is taken as the figure by which the weight of 

 caoutchouc should be divided in order to obtainn the weight of 

 the rubber from which it came. 



HASTENING EVAPORATION. 



.\ piece of lilock tin tubing is made into a coil, which is put 

 into a water bath, and to one end is attached a rubber tube con- 

 necting to a source of air. To the other end is attached a tubins 

 connected to a right-angle glass tube, and which is passed through 

 a stopper held in a clamp on a ring stand. By raising and lower- 

 ing the clamp the distance of the air outlet from the surface 

 of filtrate can be regulated. B. Freeman, of Clemson College, 

 South Carolina, states that the heated air in the coil will hasten 

 evapciration .iO per cent. 



SCHOLARSHIP IN CHEMICAL ENGINEERING. 



The Clicniists' Ckd) of Xew York City announces the estab- 

 lisluncnt of a scholarship fund, the income from which, approx- 

 imately $500 per year, is to be devoted to assisting financially 

 deserving young men to obtain education in the field of industrial 

 chemistry or chemical engineering. This scholarship has been 

 endowed by Dr. Victor G. Bloedc, a prominent manufacturing 

 chemist of Baltimore. Its benefits will be open to properly qual- 

 ified applicants without restriction as to residence, and may be 

 effective at any institution in the United States, which may be 

 designated or approved by the Chemists' Club. 



All inquiries should be addressed to the Bloede scholarship 

 committee of the Chemists' Club, 50 East 41 st street. New York 

 City. Applications for the academic year 1916-1917 should be in 

 the liands of the committee on or before June 1, 1916. 



