May 1, 1920.] 



THE INDIA RUBBER WORLD 



499 



per cent. Accordingly 60 per cent of the breaking elongation 

 was fixed as the most desirable point to which to stretch. 



EFFECT OF SUCCXSSIVE STRETCHING. 



Ten pieces of stock were broken and the average elongation 

 taken. Ten pieces of each stock were then stretched to 60 per 

 cent of this elongation held ten minutes, released and measured 

 after ten minutes. This was repeated to four stretches. The 

 results shown in Table II are each the average of ten tests: 

 T.vBLE II. Effect of Repeated Stretching on Set. 



Permanent 



Set after Each Stretch. Set by First 



, * , Stretch Fig- 



■ Stretch 1st. 2nd. 3rd. 4th. ured to Per- 



Additional Set. Total centage of 



, >■ > Set. Total Set. 



Pure gum 4 2 6 66 



Cheap friction 13 2 1 16 81 



Friction 4 2 2 8 50 



Low gravity tread 18 1 S 1 25 72 



High gravity tread 14 6 4 1 25 56 



Medium gravity tread... 19 12 8 1 40 47.5 



Cheap mechanical 22 9 8 1 40 50 



Attempts have been made to reduce the time required for 

 stretching and resting between stretches, but the results do not 

 seem quite reliable, although for routine laboratory work we 

 have used a shorter time. After using this method for two years, 

 while we do not consider it perfect, we believe it far superior 

 to any other method which has been proposed.— Earle L. Davies. 

 the value of shoddy in mechanical rubber goods. 



A chart was presented which gave the cost relations between 

 scrap rubber and reclaimed rubber. The reclaimed rubber was 

 evaluated on a basis of tensile strength and compared to a corre- 

 sponding priced new rubber. A line of demarcation through 

 the center of the chart showed where it was more economical 

 to use new rubber or reclaimed rubber. — J. M. Bierer. 



RUBBER CHEMISTRY FROM THE COLLOIDAL VIEWPOINT. 



The mechanism of crystallization, condensation, polymerization 

 and coagulation was discussed. Gelation is one type of coagu- 

 lation. Selective adsorption is given as a reason for the increased 

 tensile strength of compounded rubber. This deals with the dif- 

 ferent surface energ}^ of rubber and the various compounding 

 ingredients. — Ellwood B. Spear. 



JAR RINGS AND POISONED OLIVES. 



NrMEROus FATAi. c.\SES of poisoning due to eating olives put 

 up in glass jars have occasioned an inquiry by the United 

 States Department of Justice as to the part alleged to have been 

 played by rubber rings on jars. The president of one large 

 packing concern in California, who started the investigation, 

 claims a conspiracy by Germans during the war to poison this 

 food product. He believes that the company from which 

 he bought all its rubber vacuum jar seals for the olives 

 put up in 1917 was victimized by sympathizers of Germany; and 

 he is confident that analysis now being made by government 

 chemists of the rubber used and the toxins said to have been 

 produced in the olive solution, will confirm his claims. 



His company, he said, lost $100,000 in spoiled goods, the first 

 and only packs giving trouble being those of 1917 and 1918, and 

 in which the suspected rubber was used. He believes that some 

 enemy agents tampered with the rubber mixture in the making, 

 not only by causing it to deteriorate in a short time, but that they 

 also introduced into the rubber germs of a malignant disease. 

 As soon as the rubber gave way, air entered the jars and the 

 "bugs" produced toxins in the olives. Had the rubber been 

 "glycerined" he believes the trouble might have been lessened or 

 obviated. Careful checking, he says, showed that goods with 

 perfect seals — the same olives being used— gave no trouble at all. 



The Chicago concern which supplied the jar rings, received 

 complaints from many other purchasers about similar goods, and 

 the explanation given w^as that the company had trouble in 



getting pure rubber owing to the Government's demands for war 

 needs. 



As the federal government investigation findings may not be 

 disclosed for a year, private agencies are trying to find out on 

 their own account if it is likely the rubber seals could be poisoned 

 in the manner suspected. 



According to bacteriologists the olive-poisoning was caused 

 by a bacterium known as botulinus, first isolated by German 

 savants from spoiled sausage meat, although it is also found in 

 canned animal products which have been known to cause pto- 

 maine poisoning. It is described as obligate anaerobic, that is, 

 it thrives best when deprived of oxygen or common air, and 

 needs neither to develop a powerful toxin. It is possible, it is 

 believed, to embed spores from such bacteria in suitably pre- 

 pared rubber so that they might after a certain period and 

 under favoring conditions harmfully affect foodstuffs in contact 

 with such rubber. The fact that the spores are remarkably 

 tenacious of life lends some color to the story that the poisoning 

 was timed by enemy agencies through a rotting of rubber seals. 



Certain it is, say the bacteriologists, that dry heat at 230 de- 

 grees C. will kill the botulinus, and it can also be destroyed by 

 prolonged boiling at 212 degrees F. 



On the other hand, the processes of rubber manufacture, 

 specifically jar-ring making, are not perhaps understood by the 

 scientists. They agree that sufficient heat will kill the germ. 

 Granting that a germ-distributing German introduced the bac- 

 teria into a batch of ring stock on a mixing mill, the germs dur- 

 ing the process of mixing would be subjected to a heat equal to 

 that of boiling water for at least fifteen' minutes. If the stock 

 went at once to the tubing machine and was run off it would 

 get another fifteen minutes of the same heat. Or if the rings 

 were made by wrapping the stock in sheet form about a mandrel 

 the heat of the warmer and the calender would be considerable. 



The real exposure to heat, however, would be during vul- 

 canization. Here the germ would have to stand certainly 300 

 degrees F., say for an hour and a half, depending of course, upon 

 the grade of stock used. 



In addition to this would be the presence of zinc and sulphur, 

 which are certainly not germ food. It must be a fairly robust 

 germ, extraordinarily tenacious of life that will survive entomb- 

 ment and vulcanization in a jar ring. 



RUBBER FOOTWEAR ACTIVE. 



Present indications encourage the belief that the year 1920 

 will establish the record to date in the demand for rubber foot- 

 wear of all kinds. An exceptionally snowy winter, which did 

 not get its stride until after the new year came in, taxed manu- 

 facturers of arctics, overs and boots to capacity. With the pass- 

 ing of Easter and the coming of numerous signs of an early 

 spring, other lines came to the front. Thus far, the demand 

 for seasonable goods has been unusually large, and the variety 

 of handsome styles of rubber and fabric shoes is great enough 

 to attract many away from leather shoes for summer wear, 

 especially in view of the continued high prices of leather shoes. 



The less expensive athletic and outdoor shoes are rapidly in- 

 creasing in popularity, affording economy, durability, comfort 

 and attractiveness. Incidentally the high cost of leather foot- 

 wear is increasing the demand for overs and footholds in order 

 to protect the leather from water damage. Rubber boots are 

 becoming regarded more and more as a necessary part of every 

 man's outfit, and a comparatively new foot covering kno^vn as 

 the rubber bootee is coming into popularity. It resembles the 

 arctic overshoe, but has the quality of a rubber boot as far as 

 it goes. Thus in many ways rubber footwear in its varied forms 

 is rivaling leather footwear and for many purposes in certain 

 seasons is a very practical "substitute." 



