THE INDIA RUBBER WORLD 



[June 1, 1916. 



necessary in regard to rubber than was being practiced at 

 the present time. 



Dr. Stevens said that ^pf spme years there had been 

 research stations in Ceylo^^and Malaya. Rubber stations 

 have been carrying out work for six or seven years past, 

 and researches have also been carried out at the Imperial 

 Institute and in private laboratories. 



OXIDATION OF 'hEVEA RUBBER. 



The experiments of M. Kerbosch on the oxidizability of rubber 

 of Hcvea Braziliensis (Bulletin of .Agricultural Intelligence, 1915, 

 Vol., 6. page 1703) show that rubber under the influence of sun- 

 light and of diffused daylight gave the following resuhs : Rub- 

 ber prepared by evaporation , of the latex resists oxidation better 

 tlian that prepared by coagulation. The difference is due to the 

 presence in the former of certain unidentified soluble constituents 

 of the latex. The oxidizability .of the rubber is not affected by 

 the presence of quebrachite. The superiority of the Brazilian 

 method of coagulation is probably due chiefly to the retention of 

 the soluble constituents mentioned, and not to the smoking 

 operation. 



NEW COAGULANTS FOR RUBBER LATEX. 



HEVE.A. latex is readily coagulated when acidified. It is 

 not desirable to acconiplish this by permitting the 

 latex to become rancid because of the important loss of 

 uncoagulated rubber in the waste serum of the latex. In 

 consequence, acetic acid has been generally adopted as the 

 preferred coagulant in the preparation of plantation rubber. 



Since the beginning of the war the price of acetic acid 

 has risen from about ten cents to 60 cents per pound, and 

 is almost unobtainable owing to lack of transportation 

 facilities. 



The serious shortage thus caused has resulted in a thor- 

 ough search for a substitute for the very large quantity of 

 acetic acid required on the rubber plantations throughout 

 the Far East. Among the substitute reagents suggested but 

 not generally adopted are sulphuric, hydrochloric, nitric, 

 oxalic, tannic, carbolic, tartaric and citric acids, corrosive 

 sublimate and acid potassium tartrate. Aside from the merits 

 of these chemicals as coagulants, they are in scarcely better 

 position than acetic acid as regards price and transportation 

 to the plantations. .Acetic acid can be made cheaply and in 

 ample quantity from cocoanut shells. The crude product is 

 not sufficiently clear in color for the coagulation of rubber 

 that is to be made into first latex crepe, but good, clear, 

 smoked sheet can be and is being made in large quantities 

 with it. 



For the production of first latex crepe a better substitute 

 for glacial acetic acid is necessary. This has apparently 

 been found. It is well known that in all parts of the tropics 

 there are many strongly acid fruits, water extracts of the 

 juices of which readily coagulate rubber latex. Shortly after 

 the beginning of the war cocoanut water, and cocoanut vine- 

 gar were found to jje suitable coagulants; especially cocoanut 

 water, which is ri6w being regularly used on some rubber 

 estates. The process consists in allowing the cocoanut water 

 to ferment for four or five days, after which it can be used 

 immediately for coagulating latex. It is said to produce 

 better rubber than that procured by using crude acetic acid, 

 especially as regards color. 



Ceylon is said to produce enough cocoanut shells to provide 

 sufficient acetic acid for all the smoked sheet rubber made 

 in Ceylon and perhaps in the whole East. At the same time 

 the available supply of cocoanut water would doubtless 

 practically supply the requirements for the production of 

 first latex rubber, and the entire rearrangement become a 

 profitable one both to growers of cocoanuts and of rubber. 



PROPERTIES OF VULCANIZED RUBBER. 



' I ' 1 1 li relation-ship of mechanical Ao chemical properties of 

 ■*■ vulcanized rubber has been studied by Philip Schidrowitz 

 and H. D. Goldsbrough, who have published in the "India Rub- 

 ber Journal" (April 8) notes on the preliminary results obtained. 

 The experimental methods employed were as follows : 



Mixing. — Standard mixing of lOOjiarts rubber and 8 parts 

 sulphur. 



Curing. — Standard cure, in screw rfiolds, in live steam at 

 286 degrees F. 



Correct Cure (Rate of cure;. — This was determined by the 

 optimum curve method ("Rubber Industry," 1914, page 212). 



The examination of many hundreds of samples demon- 

 strates that the optimum curve method of estimating the 

 correct cure gives in practice concordant results, and actually 

 represents the best product obtainable under the conditions 

 of mixing, curing and testing. 



Slope of Curve (Type). — As a matter of convenience the 

 slope of curve is represented by the figure corresponding 

 to the expression 



E, — E 



T = 



2.5 

 E ==: elongation at a load of 600 grams per square millimeter 

 and El = that at a load of 1,040 grams per square millimeter. 

 For any given load the extension will be greater for the 

 Matter curve. This fact is of fundamental importance. 



Insoluble M.\tter. — This was determined by difference [Schid- 

 rowitz, "Rubber" (Methuen, 1911), p. 252]. 



Soluble Matter. — Caspari's method, and his distinction be- 

 tween "soluble" and "pectous" rubber was observed. 



Combined Sulphur. — This was estimated in the rubber after 

 exliaustive extraction with acetone. 



I I £? ^s Is U-^ |S |l lis 



I S. i35 Kfc 3t? i2i;2 ,ss cgs ^cgi 



1— Smoked sheet... 2 38 2,118 X 10.39 10.80 81.9 4.37 



2— Smoked sheet. . . 2'4 33 2,250 X 10.74 8.88 81.3 4.86 



3— Plain sheet ZVi 33 2,100 X 10.06 7.52 28.8 2.88 



4— Plain sheet 4 31 2,450 X 11.00 6.64 80.55 2.03 



5— Smoked sheet... 13^ 36 2,100 X 10.43 11.52 81.1 4.30 



6— Smoked sheet... 2 37 2,110 X 10.35 10.16 76.4 4.70 



7— Film sheet 2'A 37 2,528 X 10.56 7.52 94.85 4.21 



.S— Film sheet 1 J4 33 2,289 X 10.78 - 17.20 81.75 4.70 



9— Para 3 38 2,093 X 10.43 3.62 



As far as they go, these results do .not support the sug- 

 gestion made by B. J. Eaton that the amount of combined 

 sulphur at the correct rate of cure may be more or less a 

 constant, like the mechanical properties, It should be noted 

 that the two plain sheet samples, while not differing greatly 

 as regards mechanical properties from the smoked sheet 

 samples, both show a very much lower "combined" sulphur 

 content. 



On March 23, the corner stone of the new chemistry building 

 of the Bureau of Standards, at Washington, D. C, was laid by 

 the Hon. William C. Redfield, Secretary of Commerce. The 

 building is about 60 X 200 feet, constructed of brick and stone, 

 and is to be four stories in height, in addition to attic and base- 

 ment. It will provide adequate laboratory space for about 120 

 chemists, besides rooms for offices, supplies, etc. It will probably 

 be ready for occupancy early in the spring of 1917. 



Replete with information for rubber manufacturers 

 Pearson's "Crude Rubber and Compounding Ingredients.' 



