72 



THE INDIA RUBBER WORLD 



[NOVEMIIKR 1, 1916. 



absolute alcohol and then wash thoroughly with hot water. 

 Wash any rubber on the filter paper back into the original flask 

 and reserve this foi the determination of rubber hydrocarbons. 

 Evaporate the solution to appro.ximate dryness, take up in warm 

 water and transfer to a separatory funnel, .•\cidify with 30 cc. 

 5 normal hyilrocliloric acid, usiuR this to rinse the hcaker. 

 Add suflicient water to make the bulk of the solution 100 cc. 

 When cool add 40 cc. ether, using it to rinse the beaker in 20 cc. 

 portions. Shake the aqueous and ethereal .solutions thoroughly. 

 After complete separation, draw off the aqueous solution and 

 treat in another separatory funnel, with a fresh 20 cc. portion 

 of ether. Continue to shake the aqueous solution with fresh 

 portions of ether until a colorless portion has been obtained. 

 then shake out twice more. Unite the ethereal solutions and 

 wash with successive additions of water, continuing twice after 

 the water shows no acid reaction. Filter through a plug of ex- 

 tracted cotton into a tared flask, wash the filter and funnel 

 with ether, evaporate the ether without boiling and dry the 

 residue at 95 to 100 degrees C. Cool in a desiccator and weigh. 

 Continue to dry until constant weight is obtained. 



RUBBER HYDROCARBONS. 



Section 29. Add to the flask containing tlie rubber residue 

 from the alcoholic potash extraction, sufficient water to make 

 the total volume of the solution 125 cc. and then add 25 cc. con- 

 centrated hydrochloric acid. Heat for an hour at 97 to 100 

 degrees C. Decant the supernatant liquid through a hardened 

 filter paper on a Buchner funnel 7 cm. in diameter, using suc- 

 tion ; wash the residue with 25 cc. hot water and decant. (While 

 a Buchner funnel is recommended, it is permissible to use an 11 

 cm. hardened filter paper with platinum cone, in a 60 degree 

 funnel). Perform this entire treatment with water and hydro- 

 chloric acid, three times and save the first and second decanta- 

 tions for the "organic matter" test described in Section 36. The 

 rubl)er at this stage should be white and practically free from 

 black specks of undissolved fillers : if not, continue the acid 

 treatment until the 1)lack specks disappear. (If carbon is present, 

 all the particles of rubber will be grayish, bluish, or black, de- 

 pending on the form and quantity of carbon used. Black specks 

 in light particles of rubber usually indicate the presence of lead 

 sulphide which must be removed to prevent the formation of 

 lead sulphate on igniting the residue C. Add 150 cc. hot water 

 to the flask and let stand on a steam bath or hot plate for half an 

 hour and decant through the filter paper. Return to the flask 

 any rubber that goes on the filter paper. Repeat until the wash- 

 ings are free from chlorides (See Section 36). Transfer all the 

 rubber in the flask to the filter paper and dry as much as possi- 

 ble by suction. Wash the rubber with 50 cc. of 95 per cent 

 alcohol, using suction. Transfer the entire residue to a weighing 

 bottle. Dry at 95 to 100 degrees C. for an hour, cool in a vacuum 

 desiccator under reduced pressure and weigh. Dry for a half 

 hour, cool and weigh, re|)eating this process until either constant 

 weight is reached or the weight starts to increase. Let this 

 weight be represented by C. On a portion D of this residue C 

 determine the ash E, according to Section 30 and the sulphur F 

 in the ash E. Determine the sulphur H in another portion G 

 of residue C. Make all sulphur determinations as described 

 under "Total Sulphur." 



Section 30. Place about 0.5 grams of residue C into a weighed 

 porcelain crucible. Let the weight of residue be represented by D. 

 Heat gently, gradually driving off the volatile matter. When the 

 crucible has ceased to smoke, raise tlie temperature gradually to 

 between 450 and 500 degrees C. until all organic matter has been 

 burned away, which is usually indicated by the ash becoming 

 white. (An electric muffle furnace with pyroareter is recom- 

 mended for this purpose.) Cool in a desiccator and weigh, the 

 weight of ash being represented by E in the formula for rubber 

 hydrocarbons. Make sulphur test on ash by the method de- 

 scribed under "Total -Sulphur." If, however, 50x CxE is not 



over unity, the determination of sulphur in the ash may be 

 omitted and /•" assumed to be zero. 

 Then, 



Rubber Hydrocarbons = 100 



r E-F H-] 



expressed as a percentage of the total sample. 



TOT.M. sri.l'IiriJ. 

 Section 31. Place 0.5 grams of rubber in a porcelain ciucible 

 of about 100 cc. capacity, .^dd 20 cc. nitric acid-bromine reagent, 

 cover the crucible with a watch glass, and allow to stand for one 

 hour. Heat very carefully for an hour, remove the cover, rinsing 

 it with a little water, and evaporate to dryness. Add 5 grams 

 of the KNO3 — Na-COa fusion mixture, and 3 to 4 cc. of distilled 

 water. Digest for a few minutes, and then spread the mixture 

 half way up the side of tlie crucible to facilitate drying. Dry on 

 a steam bath or hot plate. Fuse the mi.xture, using a sulphur- 

 free flame until all the organic matter has been destroyed and the 

 melt is quite soft. x\llow to cool, place the crucible in a 600 cc. 

 beaker, and cover with water. Digest three or four hours on 

 the steam bath. Filter into an 800 cc. beaker, washing thoroughly 

 with hot water. The total volume should be about 500 cc. 

 Allow to cool, add 7 to 8 cc. concentrated hydrochloric acid to 

 the filtrate, and heat on the steam bath. Test the solution for 

 acidity with Congo paper and add 10 cc. of hot barium chloride 

 solution. Allow to stand over night, filter, wash, weigh the 

 barium sulpliate and calculate to sulphur. 



I.\-rERPRET.'\TION. 



Section 34. The percentage of rubber shall be considered to 

 be the sum of the rubber hydrocarbons, saponifiable acetone ex- 

 tract, unsaponifiable resins, chloroform and alcoholic potash 

 extracts, expressed as percentages. If the chloroform extract is 

 over 3.0 per cent of the rubber so calculated, subtract the excess 

 from the rubber. If the KOH extract is over 1.8 per cent of 

 the rubber, as first calculated, subtract this excess also from the 

 rubber. 



ORGANIC FILLERS. 



Section 36. Transfer the first and second decantations of the 

 hydrochloric acid solutions to a carefully cleaned porcelain dish 

 and add 20 cc. concentrated sulphuric acid. Place dish on steam 

 bath or hot plate to drive off water and hydrochloric acid. A 

 pronounced charring of the residue indicates the presence of 

 organic matter soluble in water or hydrolyzed by hydrochloric 

 acid. 



Examine filter paper and rubber while decanting acid solution 

 and again while washing free of chlorides. Some types of organic 

 fillers not removed by water and hydrochloric acid, would be 

 plainly visible at this point. 



Place a small portion of residue C under a microscope and ex- 

 amine for fibrous and other characteristic organic material.' If 

 organic fillers are indicated and not clearly proven by this test, 

 place 1 gram of the organic sample in a beaker, add 75 cc. xylol 

 and heat on hot plate until the rubber is dissolved. Decant 

 xylol solution and wash residue with ether several times by de- 

 cantation. Dry residue and examine under the microscope. 



NEW YORK RUBBER MANUFACTURERS BUSIER. 



.According to the report of the Industrial Commission of the 

 New York State Department of Labor, the manufacturers of 

 rubber and gutta percha goods in that State employed from 16 

 to 21 per cent more workers from March to August, 19^6, than 

 were employed in June. 1915 (the basis of computation), and in 

 e:,ch of the months the increase over the same month a year ago 

 ranged from 25 to 40 per cent. The payrolls of these manufac- 

 turers ran from 33 to 41 per cent higher than the same months 

 last vear. 



