NOVE-MBER 1. 1916. 



THE INDIA RUBBER V/ORLD 



71 



Aniline differs from other solvents in that rubber dissolved 

 in it forms a thin solution which permits the mineral fillers to 

 separate r£adily. 



Samples No. i and O No. 3 are the same, except that O No. 

 2 was purposely over-cured. Sample H was prepared using the 

 same recipe but by another manufacturer. Sample H, I and / 

 were unintentionally under-cured. Sample C is a hard valve. 

 Sample G No. 14 contains caucho rubber. 



The small amount of nitrobenzene is used, because it makes 

 solution more rapid. It was found that semi-cured compounds 

 dissolve more slowly than thoroughly cured soft stocks or very 

 hard ones. With under-cured compouflds a soft, pasty mass 

 is formed, which is very slow to dissolve, while this does not 

 occur if the material is properly vulcanized. 



We found that in a few cases an additional digestion with 

 half the quantity of solvent for five hours reduced the amount 

 of mineral fillers about 0.5 per cent. In specification work it 

 is advisable to make this second digestion -after the ether has 

 been expelled from the tube by heating. 



.\nalysis of the fillers shows that the rubber as found by dif- 

 ference will. not include the sulphur of vulcanization. 



It will be noted that the sum of the percentages of rubber 

 found and organic acetone extract is slightly greater than the 

 percentage of rubber used in the recipe. 



The fillers during vulcanization and afterwards in the course 

 of analysis have combined with sulphur to form new compounds. 

 If this combination of fillers and sulphur is a substitution of 

 sulphur for son^e other acid radical, the resultant product would 

 weigh less than the sum of the ingredients entering the reac- 

 tion and the rubber found by difference would be slightly greater 

 thereby. 



We expect to continue these experiments when other samples 

 are available, and a final report will be made on the subject when 

 we have all the data at hand. 



REPORT OF THE JOINT RUBBER INSULATION 

 COMMITTEE. 



THE Joint Rubber Insulation Committee, whose preliminary 

 report was printed in The India Rubber World. February 1, 

 1915, has now completed a second report, which was presented 

 in abstract to the Rubber Section of the American Chemical So- 

 ciety on September 29 by William A. Del Mar, the secretary of 

 the committee. The second report, like the first, presents a speci- 

 fication for high-grade rubber insulation for electric wires and 

 cables, and an analytical procedure for use in connection there- 

 with. 



The specification is identical with that in the preliminary report, 

 except that the first clause is altered to read as follows ; 



"A 30 per cent fine Para or best quality plantation Hcz're rub- 



] 



her compound with mineral fillers, shall be furnished." The 

 change consists in the substitution of "best quality plantation" for 

 "smoked first latex," which appeared in the earlier report. 



The analytical procedure has been changed in two important 

 particulars, and a number of minor improvements have been 

 made. One of the changes is the elimination of the terebene 

 method, and the substitution of a modified ash method, for the 

 determination of fillers and rubber. This method is a modifica- 

 tion of one devised by G. H. Savage. A general outline of the 

 procedure is given on the diagram below. It will be seen that 

 the residues from, the alcoholic potash saponification are treated 

 with hydrochloric acid to remove organic matter, and the part in- 

 soluble in acid is dried and divided into two parts, one of which 

 is used to the determination of sulphur, and the other ignited. 

 A sulphur determination is also made on the ash. The rubber 

 hydrocarbons as a percentage of the total sample are given by 

 the following formula: 



C r E-F H 



Rubber Hydrocarbons = 100 — 1 



4 L D G 



The total weight of sample used in the determination is 4^. and 

 the letters C, D, E, F , G, and H represent the weights in grams 

 of the substance indicated in the diagram. 



The other important change is the adoption of the Bureau of 

 Standards nitric acid-bromine method for the determination of 

 total sulphur. 



.•\ qualitative test for organic fillers has also been added. 



The complete report will not be available until it has been 

 approved by the General Committee, which appointed the Joint 

 Rubber Insulation Committee. It is hoped that arrangements for 

 publication will be made in about a month. 



The Joint Rubber Insulation Committee has now been at work 

 for five years and has held 25 meetings, in addition to numerous 

 sub-committee meetings. The committee has been an active one, 

 and its influence has been widely felt, the specification and the 

 greater part of the preliminary analytical procedure being how 

 accepted as standard by electrical engineers and rubber chemists. 



The following abstracts from the report read at the meeting 

 of the Rubber Section, give the details of the determination of 

 rubber hydrocarbons and total sulphur, and should be read in 

 conjunction with the preliminary report referred to above. 

 ALCOHOLIC POTASH EXTRACT. 



Section 28. Dry the residues from the chloroform extractions 

 at 50 to 60 degrees C. until the odor of chloroform can no 

 longer be detected : unite the residues from the two 2-gram sam- 

 ples in a 200 cc. Erlenmeyer flask. .Add 100 cc. alcoholic potash 

 solution and boil for four hours under a reflux condenser. Filter 

 the solution by decantation through an 11 cm, hardened filter 

 paper into a beaker and wash twice, using each time 25 cc. hot 



Acetona EKfrc 



Two 2 arm. Sa mplsa of ffubber 



(Sapo n / ff with HO ft' 



Untaponifiab/J /Material Alkali Son/t/» Acmtene CAHuafacm 



COinoi^» "jKicoXoi) ^ extract , Ejtract 



\ (Trtat rilh IllfO^ No, O, efe.) ^' " "" ' 



Ifes/ctue 



(Ma*rm C/t/orqrorm Cttroct ion*} 



RoslduC3( United) 

 (Saponiff with HOM} 



r 



1, 



n 



Insolub le Soluble frea Saoortiflabia 



rarbons U .-vaponrflable ^fiiuf Ace ' 

 A. Material 



Hvdncarbons U.-uaponrfioble iijpiiuf Acetoria 

 Material Ertroof 



Treat witft CCi ^* ftg SO^ 



\ ' 1 



Saponif fable Extract 

 (Treat mith HCI and Etber) 



Remid u e 



(Treat with HCI « heat ) 



Hydroca rbon s Unsoponifiable 

 _^ _ ffeains 



Total Waxy Hydrocarbons -AtB 



Res l\lual KOHEitract 

 Solution 



r 



X 



iVei^h Substances tv/'f/t Names 

 Of her " by Difference 



fnso/uble 



(Wash *. eJfy) 

 (Diricfe lyi tmtoportm) 



■H 3. 



\t0nitm) Sulphur 



_j^ u 



(Su/phur) -'^ ■ 



So/ybte 



(R e se rttm for 

 Organic tmst) 



OuTLiXE OF Method of Rubber Analysis Exclusive of Total Sulphur Determination. 



