September 1, 1921 



THE INDIA RUBBER WORLD 



897 



untreated giitta percha as an insulating material. Felten und 

 Guilleaume Carlswerk A.-G. German patent No. 303,871, April 

 15, 1916. 



the highest 8'/" cents. The average quotation for the entire year 

 was 7.9 cents. 



OTHER CHEMICAL PATENTS 



GERMANY 



PATENTS ISSUED, WITH DATES OF ISSUE 



J40,491 Ijamiary 27, 1920) Process fur viilc.iiiizing rubber and similar 

 substances. The Dunlop Rubber Co., Limited, London; 

 represented by R- H. Korn, Berlin S. W. 11. 



LABORATORY APPARATUS 



USE OF ALUNDUM FOR FILTRATION 



THE alundum filters, funnel and crucible, have many advantages 

 over the old funnel, filter paper and porcelain crucible in that 

 there is no carbonaceous matter to reduce the precipitate when it 

 is ignited. However, the filtration of finely divided precipitates 

 is difficult except in the finest grades and sometimes they do not 

 retain the precipitate. They are also slow if there is much of 

 a precipitate. The same can be said of the old Gooch crucible 

 when its asbestos mat becomes filled with precipitate. 



Therefore, to speed up the filtration, retain the finest precipitates 

 and do away with the reduction of the precipitate, the following 

 method was devised : 



A thin asbestos mat, just enough to cover the holes, is put into 

 an ordinary Gooch crucible. Then "RR" alundum powder, 90- 

 mesh, alkali free, for carbon determinations, is put in to form a 

 mat about one-quarter of an inch deep. It is then washed with 

 a wash bottle until the surface is flat. The whole is then dried 

 in the oven, when it is ready for use. 



Care should be taken when the precipitate is poured into the 

 ■filter not to wash the alundum away from the sides. The alundum 

 should be covered with precipitate before the suction is applied. 

 After filtration, the Gooch is dried or ignited as desired. This 

 method has been found much faster and more efficient than any 

 of the regular methods of filtration. — I. C. Guest in The Chemist- 

 Analvst. 



HOME-MADE POLICEMAN 



The home-made policeman herein described has given good 

 service. Close one end of a piece of rubber tubing with a tight- 

 fitting solid-rubber plug (one of the "cores" obtained in boring 

 rubber stoppers) and slip the other end of the tube onto a glass 

 rod until the rod meets the plug. With a sharp knife cut through 

 the tube and plug so as to produce a smooth, flush end surface and 

 leave about one-half inch of the plug in the tube. 



Incidentally the cores cut from rubber stoppers come in handy 

 for a variety of purposes, such as closing the ends of glass tubes, 

 for which none of the standard stoppers are small enough, plug- 

 ging up the holes in rubber stoppers, etc. They are especially 

 valuable as a substitute for the usual glass plug for closing the 

 end of the Bunsen valve tube in a wash bottle. These tubes be- 

 come "dead" and loose after long use with boiling water, and fall 

 into the wash bottle. Where glass plugs are used a broken bottle 

 sometimes results. — Seth S. Walker in The Chemist-Analyst. 



UNITED STATES LITHOPONE PRODUCTION 



It is estimated that the rubber industry consumed 7,700 tons of 



lithopone in 1919. The quantity, value and average selling price 



of lithopone marketed in the United States in 1919 and 1920 



follows : 



Averatre Sales 

 Year Short Tons Value Price Per Ton 



1919 78.365 $10,218,850 $130.40 



1920 89. .17.1 12.484,925 139 69 



Increase 1 1.008 2,266.075 9.29 



Percentage 14.0 22,2 7.10 



The New York market quotations showed very little variation 

 lhrous;liout 1920. the lowest price being 7J4 cents [kt pound and 



BASIC CAUSES FOR STICKINESS IN CRUDE RUBBER 

 By .\ndre Dubosc 



1 REVIEW again the work of Brindejonc, especially as his con- 

 clusions may have an excellent effect not only upon African 

 rulibers, but on Central and South American rubbers as well, and 

 perhaps upon plantation rubbers. Brindejonc's and my own ob- 

 servations are briefly summarized below. 



Sticky rubber is black, devoid of elasticity, and thereby has 

 lost the greatest part of its value. In order to determine the 

 reasons for this change, Brindejonc made a series of tests in 

 whicli he used Landolphia rubber. By extraction from the dry 

 Landolphia bark he obtained sheets of rubber, which were very 

 spongy and sensitive to the slightest causes of deterioration. 



GENERAL CAUSES OF STICKINESS 



The fulUnving factors in the deterioration of rubber were 

 studied: (1) The action of salt, which is used generally as a 

 coagulant in the Niger and Soudan regions ; (2) The action of 

 dilute acetic acid and carbolic acid, which can be formed in 

 the serum if the latex commences to ferment. (3) The action of 

 heat without light, within the liinits in which it is met in practice; 

 (4) The action of sunlight; (5) The action of diffused sunlight. 



During these experiments, a fact of great significance 

 was developed, namely, that the rubber which has been affected 

 by one or the other of the agents indicated above, continues to 

 deteriorate, even when the primary cause of the deterioration has 

 disappeared. 



Therefore when a mass of rubber begins to become sticky it 

 will continue so until the entire mass has been converted into a 

 viscous product. The goods made from this rubber are bound 

 to deteriorate in spite of vulcanization. They are even capable 

 of contaminating other manufactured rubber goods with which 

 they come in contact. 



SALT AND ALKALINE CHLORIDES HARMFUL 



Samples of standard Landolphia rubber or of Landolphia bark 

 were dipped into solutions of sodium chloride of the concentra- 

 tions 1 to 100, 1 to 250, and 1 to 500. In humid atmosphere and 

 a temperature varying from 25 to 40 degrees C, when the tests 

 were made in the dark, the action of 1 to 100 solution was ap- 

 parent at the end of 20 days. The other two solutions — 1 to 250 

 and 1 to 500 — did not have any effect until 30 days had elapsed. 

 Hence very small amounts of salt in the rubber, even when the 

 rubber is not exposed to sunlight, are able to produce the phe- 

 nomenon of sticking. 



Up to the present time no importance has been attached to 

 the presence of sodium chloride in the ash obtained by the burn- 

 ing of rubber. Brindejonc's work shows that salt, far from be- 

 ing inoffensive, is capable, although the action is slow, of causing 

 the entire mass of rubber to become sticky throughout. From 

 its outward appearance, the rubber containing salt is apparently 

 in a good condition. 



It is of the highest importance, in analyzing old rubber, to de- 

 termine its sodium chloride content, for its tendency to stick is 

 a direct function of its salt content If this is greater than a 

 few thousandths of a per cent, the rubber should be washed 

 immediately to prevent it from becoming sticky. In using rub- 

 ber to coat f.ibrics, it is important to see whether or not the 

 sizing used in the cloth contains any traces of salt or of mag- 

 nesium chloride, which is often used for this purpose. This sub- 

 stance, just like common salt, is capable of producing the phe- 

 nomenon of sticking in rubber coatings, even though the mer- 

 chandise is placed where it is absolutely dark. 



Here is one of the causes of rubber sticking, which is very 

 little known and to which we cannot call the attention of the 



