70 



THE INDIA RUBBER WORLD 



[November 1, 1916. 



decanted through the Gooch crucible into the combustion flask, 

 repeatedly, until the filtrate runs through entirely colorless. 

 After evaporation of the acetate (recovery of the solvent as well) 

 the residue is carefully freed from solvent by warming the con- 

 taining flask in a boiling water bath for. say, 15 minutes, after 

 which 15 cc. of water containing 1 drop concentrated HCl, are 

 added, and quickly evaporated by the use of a boiling calcium 

 chloride bath and brisk current of dry air. The heating is con- 

 tinued at least one-half hour after the residue is again apparently 

 dry. 



The Co.mbustion Apparatus. This consists of a 200 cc. round 

 bottomed distilling flask, which is provided with a dropping fun- 

 nel (100 cc.) tlirough a one-holed rubber stopper, and a series 

 of U tubes containing in order: (1) concentrated HjSO, — KXr; 

 Oj, renewed every 1 or 2 combustions; (2) water containing a 

 drop of the preceding; (3) granular zinc; (4) calcium chloride; 

 (5) soda-lime (weighed) ; (6) soda-lime and calcium chloride 

 (weighed). 



The Combustion. The weighed soda-lime tubes in position, 

 and the combustion flask cooled by water, a volume (20 cc.) of 

 cooled concentrated sulphuric acid is run rapidly into the flask 

 on the nitrosite ; then the cooled oxidizing solution of 10 

 grams pulverized K,Cr;0, in 75 cc. concentrated HjSO,, in a very 

 slow stream. The flask may now be gently warmed by a sand 

 bath to obtain a moderately rapid evolution of gas.* This is 

 done as long as gas continues to be evolved (about one hour). 

 when a carbon dioxide-free current of air, the heating being 

 maintained, is passed via the dropping funnel through the appara- 

 tus for at least one-half hour to sweep all carbon dioxide into 

 the soda-lime tubes. ■ 



136 



Weight CO. X X 200 gives percentage C,,. H,« in the sample. 



440 

 We hope, in conclusion, that further study and improvements 

 of this method will eventually give a reliable and not too difficult 

 procedure for the direct determination of rubber, not only in 

 good quality compounds, but also in factice and other inferior 

 substitute-containing rubbers. 



*TIiat carbon monoxide is formeci iluring the combustion can be shown 

 by allowing the gases which have pass:d the absorption train to come in 

 contact with heated copper oxide and then barium hydroxide solution. A 

 precipitate ensues, but the amount is not appreciable for the results of 

 the analysis. 



ANILINE METHOD FOR DETERMINATION OF 

 MINERAL FILLERS IN RUBBER. 



By Olio H. Klein, John H. Link and Frank Gollsch. 



ALTHOUGH the use of aniline as a solvent for vulcanized 

 rubber is not new, there is very little information to be 

 found concerning it in the literature. We have therefore thought 

 that an account of the method as far as it has been worked out, 

 together with some analyses of samples of known composition, 

 would be of interest. 



This report should be considered as a preliminary one, as the 

 supply of rubber mixings at hand was limited and other rub- 

 ber fillers are yet to be experimented with. 



In making the determination it is essential that the sample be 

 finely powdered (20 mesh). A one-gram sample is extracted 

 with acetone for four hours, dried at a low temperature, and 

 then transferred to a weighed 100 cc. centrifuge tube. It is cov- 

 ered with 50 cc. of pure aniline and 5 cc. of nitrobenzene, stirred, 

 covered, and heated at 160 degrees C. with occasional stirring 

 until solution is complete. 



It is our practice to heat the samples over night in a Freas 

 oven, and in most cases the samples are completely dissolved 

 by the ne.xt day. Sometimes the sample dissolves in three to four 

 hours. If the rubber is not yet in solution, it can be seen by 

 stirring with a glass rod. When solution is complete, there is 

 nothing to be seen but fine pigment, free from rubbery appear- 

 ance. 



The chemist who makes the analysis for the first time may be 

 uncertain of himself at this point, but after one or two deter- 

 minations have been made he will at once recognize any undis- 

 solved rubber. 



The tube is allowed to cool sufficiently, filled up with ether 

 and well stirred. It is then centrifuged for 15 minutes at 1,500 

 R.P.M. 



The supernatant liquid is decanted, about 25 cc. of ether added 

 and the pigment stirred up completely. It is centrifuged again 

 and the decantate added to the first. Four washings with ether 

 are sufficient. The tube is dried at 100 degrees C, cooled and 

 weighed. The imited decantates are evaporated and then ignited 

 in a weighed porcelain or silica dish. The weight of fillers in 

 it is added to that in the tube. 



The percentage of fillers plus that of total acetone extract is 

 subtracted from 100 per cent, and the difference recorded as 

 rubber gum. 



Sulphur 

 Zinc Oxide 



Light Magnesia Carbonate 



Hydrated Lime 



Litharge 



Whiting 



Lithopone 



Vermilion 



Carbon Black 



Golden Antimony . . . 

 Magnesium Oxide . . . 

 Aluminum Flake .... 

 Sublimed White Lead 



Asbestos 



Plumbago 



Cure. . . 



ANALYSES OF SAMPLES BY ANILINE METHOD. 



O So. 1 



Pure Rubber (Fine) 40.3 



2.0 

 18.9 



White Lead (Dutch) 18.9 



9.9 



2.0 

 8.0 



inutes 

 Pressure 



( M 



( Pressure or temperatu 



Fillers Found } 5I 71 



Organic Acetone Extract 1.09 



Free Sulphur 0.42 



Rubber 39.75 



Fillers in Dish ! g.lO 



20 



40 lbs. 

 76 



90 



40 lbs 



59.36 



59.43 



1.23 



0.20 



39.17 



0.18 



0.35 



100 



250° 



58.72 



58.40 



1.03 



0.97 



39.44 



0.47 



0.82 



26.0 

 20.0 



10.0 



100 



250° 



55.00 



54.70 



1.31 



4.50 



39.34 



0.00 



0.09 



15.0 



5.0 

 17.0 



100 



250' 



67.03 



67.79 



0.74 



2.24 



29.60 



8.21 



5.51 



F. 



33.0 



0.99 



0.88 



39.53 



0.32 



80 



30 lbs. 

 58.60 



130 



■ 38 lbs. 

 57.56 

 57.40 

 1.19 



■^9.33'-^ 

 9.32 

 6.95 



60.03 



1.29 



1.82 



36.85 



0.44 



26.67 



0.80 



0.30 



24.79 



1.43 



10.0 



20.0 



11.11 



8.89 



60 



60 lbs 



74.11 60.44 



5.04 



1.48 



33.04 



3.60 



^a/cho Rubber. 



