August 1, 1912.1 



'HE INDIA RUBBER VVOKLU 



543 



PASSAGE OF HYDROGEN THROUGH RUBBERED 

 AEROSTAT FABRICS. 



I N a communication from M. G. Austerwcil, presented to the 

 * French .Academy of Sciences in January, last, attention is 

 called to the fact that the escape of hydrogen through rubberized 

 fabrics, has long been attributed to the diffusion of the gas 

 through the pores of the rubber. This supposition, it is added, 

 may have been correct as to fabrics in which the rubber is de- 

 teriorated by resinification, but if the covering is intact, or when 

 tested only shows slight escapes, it will still be found that after 

 the aerostat has been inflated for 25 to 70 days, according to the 

 season and temperature, there is an escape of hydrogen through 

 the fabric and a simultaneous entrance of air, as Graham has 

 demonstrated in the past. 



Experiments on the fabric of the "Astra-Torres" balloon have 

 demonstrated that its impermeability is essentially variable with 

 the duration of its inflation — that is, with the length of time it 

 has been in contact with the hydrogen. The fabric regains its 

 impermeability some time after deflation has taken place. 



As the loss of gas is a reversible phenomenon it therefore 

 cannot, it is added, be attributed to a change in the rubber, which 

 is irreversible. 



Under these circumstances, it becomes necessary to seek the 

 real cause in a reversible phenomenon, which takes place in the 

 body of the fabric. This is nothing else than the absorption of 

 the hydrogen by the rubber. It is, morover, known from Ditt- 

 mar's researches that rubber absorbs certain gases, while Reych- 

 ler has demonstrated such to be the case as to sulphurous 

 anhydride. 



After a certain period of inflation the covering no longer con- 

 sists of pure rubber, but of a combination of rubber and hy- 

 drogen, in which osmosis becomes possible and is all the more 

 intense, according to the greater proportion of hydrogen. This 

 proportion increases with the duration of the contact between the 

 hydrogen and the rubber ; therefore with the duration of the in- 

 flation of the balloon. 



If the aerostat :s then deflated, the fabric, impregnated with 

 hydrogen, will, on being tested, show a very considerable escape, 

 but as the covering of rubber remains in contact with the air, the 

 rubber-hydrogen combination will be decomposed, the hydrogen 

 will be thrown off, and by degrees the fabric will regain its 

 original impermeability. 



PROPOSED FRENCH OFFICIAL RUBBER 

 LABORATORY. 



MANY of the questions affecting raw silk being more or less 

 applicable to crude rubber, it is of interest to note that 

 M. G. Vernet, the rubber expert, recently paid a visit of inspection 

 to the Lyons Condition des Soies, or official silk laboratory, where 

 the percentage of humidity' in silk is officially defined. The 

 process consists in the preliminary determination of the abso- 

 lute dry weight, by submitting samples to t'ne influence of heat 

 until every particle of moisture is extracted. For the purpose 

 of establishing the "condition weight" for which the buyer pays, 

 an addition is made representing 9 per cent, of natural moisture, ^o 

 that when silk is exceptionally dry the condition weight exceeds 

 the original weight. Various other tests of the count of the 

 silk, its elongation and other points, are not applicable in their 

 present form to rubber, but the principal test, that of moisture, 

 is one which applies to both materials. 



According to the French system, the silk conditioned is ware- 

 housed under the responsibility of the condition house, so that 

 the certificate of the condition weight becomes practically a 

 guarantee for the buyer that the silk he is receiving weighed 

 so much at a given date. 



In addition to the weight, the condition house, according to M. 



\"ernet's suggestion, would report on the shape, thickness and 

 color of the rubber, loss in washing and the appearance and 

 color of the washed rubber after drying. Other points to be 

 reported upon would include the proportion and nature of resins 

 soluble in acetone, proportion of oxygen in the washed rubber; 

 proportions of azote and albuminoids. These results would per- 

 mit the definition of the proportion of pure rubber. The nature 

 and percentage of ash would also be shown, as well as the re- 

 sistance to heat in a stove at 55 degs. C. (131 degs. F.), and 

 the plasticity of the washed rubber. The height of rebound of a 

 ball dropped from a given height would also be noted. 



Among other tests which M. Vernet suggests being made by 

 the condition house are : viscosity of solutions, solubility of rub- 

 bers in dift'erent re-agents, adhesive properties of natural rub- 

 ber and of rubber obtained by the evaporation of the solvent, as 

 well as dynamometric and mechanical tests. 



Condition houses of the same nature as that of Lyons, are 

 established at the principal centres of the European silk indus- 

 try : as well as in New York. 



GUARANTEES OF RUBBER TRANSMISSION BELT- 

 ING. 



A S already recorded, a comn;ittee was appointed at the re- 

 *^ cent congress of German Rubber Goods JNIanufacturers to 

 investigate the question of introducing uniform terms of. guar- 

 antee for rubber transmission behing. 



In discussing this subject, since the appointment of the above- 

 named committee, a writer in the "Gummi Zeitung" defends the 

 proposal on the ground that while a general guarantee of serv- 

 iceability is aft'orded by the law, the valuable character of vari- 

 ous manufacturing accessories, such as belting, justifies the 

 demand for specific guarantees. Purchasers will never be satis- 

 fied with a mere guarantee of regular and faultless quality. They 

 require an engagement to replace the belting, in case it proves 

 unserviceable before the expiration of the period for which it is 

 guaranteed, when it has been subjected to ordinary wear. 



In the interest of the belting manufacturer, where replace- 

 ment is being provided for, a special stipulation is considered 

 advisable for careful treatment and regular usage. The party 

 using the belting will, as a rule, never be disposed to admit 

 negligence in its treatment, while it is usually difficult for the 

 manufacturer to adduce such proofs on that subject as will re- 

 lieve him from responsibility. With rubber belting a good many ■ 

 causes of trouble can be foreseen, and the opinion is expressed 

 that cases attributable to faulty usage should be specifically ex- 

 cepted. Such cases, for which the maker of the belting should 

 not be held responsible, include defective arrangement or work- 

 ing of the pulleys, or defects in the pulleys themselves. Where 

 such stipulations are made, the user will naturally see, when the 

 belting is being installed, that the pulley-bearings and other me- 

 chanical accessories are in proper order. A good deal is gained 

 by such a precaution, as otherwise the guarantee might prove 

 misleading. 



With regard to the duration of the guarantee, that question, 

 it is remarked, is less important than the correct definition of the 

 responsibilities undertaken. The unfavorable consequences of 

 guarantees sometimes reported, are usually the result of too low 

 a price with too long a guarantee. In conjunction with the lat- 

 ter there should be a price paid which would allow of a proper 

 selection of material, the quality of rubber belting exercising, 

 of course, a marked influence upon its durability. The duration 

 of the guarantee would naturally be longer in a hi.gh-priced 

 quality than in a cheap belting. By making the guarantee de- 

 pendent upon the price, the belting manufacturer will be spared 

 much anxiety. In any case the minimum guarantee of six 

 months calls for a quality not to be made of every cheap ma- 



