February 1, 1917.] 



THE INDIA RUBBER WORLD 



277 



Interesting Letters from Our Readers. 



OCOTILLO VALUABLE AS A COMPOUNDING 

 INGREDIENT. 



To THE Editor of The India Rubber World : 



DEAR SIR — My attention was just called to the fact that a 

 clearer explanation should be given about the uses of oco- 

 tillo gum, also a reply to the questions asked at the conclusion 

 of the article that appeared on page 75 of the November issue of 

 The India Rubber World. The exploitation of ocotillo gum 

 reminds me of a similar experience that I had in 1907, when I 

 worked out an insulating compound using mineral rubber known 

 as No. 620 that answered the underwriters' specifications and 

 kept the cost of the compound down. 



In reference to ocotillo gum, L. B. Johnson, of Mesa, Arizona, 

 asked my opinion of it, and I told him I could not give an 

 answer until I had made a few experiments. 



The experiments were very satisfactory, as the enclosed sam- 

 ple is a cement stock compound vulcanized 45 minutes at 40 

 pounds pressure, and composed of smoked sheet, ocotillo gum, 

 M. R. X., zinc oxide, white lead, litharge and sulphur. I used 

 20 per cent of the ocotillo gum in the compound, and find that 

 it vulcanizes without any objectionable features, as is often true 

 of many new gums. 



It provides an excellent gum to add to all friction stocks 

 as it has the valuable power of causing the rubbers commonly 

 used in friction stock to make a better union by penetrating the 

 intricacies of the fabric. This is one of the very valuable char- 

 acteristics of guayule, long known to tlie rubber trade. 



At first rubber manufacturers did not look on guayule with 

 favor, but today the opposite is true. Ocotillo gum, in conjunc- 

 tion with M. R. X., guayule and a good grade of automobile 

 tire reclaim, produces a remarkably strong adhesive friction 

 stock. Ocotillo has also been found to be a very valuable in- 

 gredient in the manufacture of a substitute for leather shoe soles 

 for which there is a great demand ; also in cements and repair 

 stocks for automobile tires. Two tires are now in service re- 

 treaded with a tread stock compounded with 20 per cent of 

 ocotillo gum and smoked sheet. One of these tires has traveled 

 on the front wheel of a jitney bus over 5,000 miles; the other 

 is on a private car. 



Ocotillo gum cannot be used alone in the manufacture of this 

 or similar goods, but it does possess the very valuable property 

 of helping to make a better union, thus preventing separations in 

 many cases, and it has a valuable part to play in the greatest 

 of all businesses, the rubber industry. E. \V. Snyder. 



Los Angeles, California, December 19, 1916. 



AN ALCOHOLIC POTASH EXTRACTION METHOD. 



To THE Editor of The India Rubber World; 

 y^EAR SIR — Your readers will perhaps be interested in my 

 ^-^ recent investigations indicating a satisfactory method to 

 pursue when the analysis of vulcanized soft rubber is required 

 for specification, or especially for compound analysis. 



A known rubber compound containing 10 per cent sulphide, 

 fatty substitute and 40 per cent rubber, the remainder being sul- 

 phur and mineral fillers, was taken for the experiment. As it is 

 necessary to reduce the rubber sample to small particles in order 

 to obtain correct results, this compound was first cut with a pair 

 of scissors into the smallest possible pieces. After acetone and 

 chloroform extraction it was boiled for four hours with normal 

 alcoholic potash solution under a reflex condenser. The fatty 

 acid was then determined in the usual way, and only 45 per cent 

 of the total theoretically expected amount was obtained. Repe- 

 tition of the same procedure with two more samples yielded simi- 



lar results. Another was tried and also cut into small pieces 

 with scissors as before, but was boiled for eight hours with nor- 

 mal alcoholic potash solution, when 56 per cent of the expected 

 amount was obtained. 



By taking the same compound, however, breaking it down 

 carefully between mixing rollers, and sifting it through 32-mesh 

 screens, 92.82 per cent of the theoretical value was obtained after 

 acetone and chloroform extraction and boiling with the alcoholic 

 potash solution for only three hours. 



Passaic, New Jersey. D. Repony. 



A MENACE TO THE BOLL WEEVIL? 



To THE Editor or The India Rubber World : 



DEAR Sir — In your January issue a correspondent writes 

 that the boll weevil, advancing at the rate of 65 miles 

 annually, has now covered half of Florida and threatens the 

 Sea Island cotton crop of Georgia. He has overlooked the fact, 

 however, that the latter state holds the record for annual num- 

 ber of lynchings. Sure and awful treatment is dealt out to 

 pests of every sort; a punishment more terrible than the crime 

 never seems to be wanting, and the boll weevil may well hesi- 

 tate before penetrating far beyond the Florida boundary. Al- 

 ready the convention of Georgia, Florida and South Carolina 

 cotton growers, to be held at Valdosta, .Georgia, to-day, indi- 

 cates an inclination on the part of the State Board of Entomology 

 to take an active hand in giving this latest offender a warm 

 reception. 



Admittedly the boll weevil is a menace that must be fought 

 energetically, but meanwhile let us be hopeful of the future. 



Optimist. 



New York City, January 24, 1917. 



ACCELERATED AGING TESTS NOT YET OF VALUE TO THE CONStmEB. 

 The stenographic report of E. A. Barrier's remarks on this 

 subject before the Rubber Section of the American Chemical 

 Society, as published in The India Rubber World of December 

 1, 1916, does not exactly agree with Mr. Barrier's opinions on 

 this subject, and it is, therefore, a pleasure to give space to his 

 corrected version which follows : 



I am quite sure that every consumer wishes to get all of the 

 cooperation he can from the manufacturer, but apparently this 

 aging test is not yet in a condition where it will be of much value 

 to the consumer. It is very evident that no definite conclusion 

 can be drawn in general as to the probable life of rubber from 

 the aging test. What the consumer wants is a test that is abso- 

 lutely definite; if a sample shows up well after a few days' ex- 

 posure, he wants to be sure that it will have a certain number of 

 years of life. 



As I understand it, in the accelerated aging test a sample may 

 show good results in a ten-day test, but the ten-day sample may 

 last a shorter time in service than a three-day sample. In 

 Other words, the test appears to be of value to the manufacturer 

 where he is comparing compounds of the same type, but it does 

 not seem to be of value to the consumer for general application. 



There has been a good deal of discussion regarding this test 

 in connection with insulated wire, and it may be that when used 

 in conjunction with detailed specifications, such as those applying 

 to this class of material, the test would be of value. Tlie specifi- 

 cations call for certain chemical and physical requirements which 

 limit the manufacturer to a considerable extent as to the charac- 

 ter of compound which he can use. Under such conditions, 

 where chemical and physical requirements are retained in con- 

 junction with tlie aging test, it may be that the latter test is of 

 value. On the other hand, it certainly is not clear that the aging 

 test has developed to a point where it can be used as a substitute 

 for the ordinary chemical and pliysical requirements which now 

 generally appear in specifications. It is possible that a study of 

 chemical tests on samples which have been subjected to the aging 

 test will still further enhance its value. 



