May 1. 1919.] 



THE INDIA RUBBER WORLD 



WEIGHTS OF RUBBER TUBING. 



Sv /•. /-. Pinkham. 



THE accompanying table of weights of cylinders of water 

 has been prepared to facilitate the computation of theoretical 

 weights of rubber tubing of one inch outside diameter and 

 smaller. Rubber tubing is usually specified by the inside diame- 

 ter and wall thickness and the following is an example of the 

 method of using the table : 



Required the theoretical weight of 100 feet of tubing 9/32- 

 inch inside diameter bv 1/16-inch wall having a specific gravity 

 of 1.77. 



Inside diameter of tubing plus twice the wall thickness = 

 9/32-inch -|- 1/16-inch -{- 1/16 = 13/32-inch = outside diameter 

 of tubing. In column "B" we find 13/32-inch and opposite this 

 diameter in column "H" it is found that the weight of a cylinder 

 of water of the same diameter 100 feet long is 5.614213 pounds. In 

 column "H" opposite 9/32-inch it is found that the weight of a 

 cylinder of water of that diameter 100 feet long is 2.691024 

 pounds. Subtracting the smaller cylinder from the larger we 

 have: 5.614213 — 2.691024 = 2.9233189 and this multiplied by 

 the specific gravity, /. c. 1.77, := 5.174 pounds, the required 

 weight per 100 feet. The weight per 100 feet being found, it 

 is of course easy to find the weight of any number of feet. 



From this it will be seen that, the specific gravity being given, 

 the theoretical weight of any of the 2016 sizes of tubing within 

 the range of the table may be computed rapidly and accurately. 



64ths. 



1.. 



11 



12 



13 



14 



15 



16 



17 



IS 



19 



20 



21 



22 



23 



24 



25 



26 



27 



28 



29 



30 



32;;;!! 



33 



34 



35 



36 



37 



58 



39 



40 



41 



42 



43 



46!!!!! 

 49!!;;; 



50 



51 



52 



53 



THE INFLAMMABILITY OF GAS BLACK.' 



By Alan Lcighton, assistanl chcinist of the Bureau of Mines. 

 'T'HE following is an account of inflammability tests made on 

 *■ a sample of gas black submitted to the Bureau of Mines by 

 The B. F. Goodrich Co., Akron, Ohio. It is likely that this 

 gas black was produced by the incomplete combustion of natural 

 gas. The sample was first sent to the coal laboratory for the 

 analysis regularly given to coal dusts which are to be tested 

 for explosibility. The results of the analysis of the sample as 

 received follow : 



Cent /'!! 



'-™'- Cent. 



Moisture 1.66 Fixed carbon 92.04 



It is to be noted froiu this analysis that the volatile content 

 is very low, also the moisture content. It was impossible to 

 obtain a true size-test since the material balled up and would 

 not pass through the screens. Microscopic examination shows 

 it to be very finely divided. 



GENERAL DISCUSSION OF THE EXPLOSIBILITY OF THE DUST. 



It has been established in the experimental mine of the 

 Bureau of Mines at Bruceton, Pennsylvania, that a mixture of 

 200-mesh Pittsburgh coal dust with shale dust, in the propor- 

 tion of 30 per cent coal to 70 per cent shale, will propagate an 

 explosion. The volatile content of this mixture is about 12 

 per cent, nearly 100 per cent higher than that of gas black. 

 While this coal dust mixture is about IS per cent carbon, the 

 gas black is 85 per cent carbon. It is apparent, that if the gas 

 black is explosive, its explosive properties will be due to the 

 finely divided carbon rather than to the volatile content. Gen- 

 erally speaking, the finer a dust, the more easily it is ignited. 

 In connection with certain factory explosions, C. Engler' has 

 recorded experiments on the inflammability of soot. He could 

 not explode a mixture of air and soot, but found that a mixture 

 of gas and air otherwise non-explosive could be made to explode 

 by introducing a soot cloud. 



EXPERIMENTAL WORK. 



To get a relative idea of the inflammability of the dust, a 

 cloud was blown from a glass tube across the flame of a Bunsen 

 burner. No inflammation was obtained, the particles directly 

 in the flame appeared to burn. This seemed to indicate that 

 considerable difficulty would be encotuuered in getting an igni- 

 tion of the dust. 



Tests were then made with the Clement-Frazer apparatus. 

 This apparatus (described in Technical Paper 141 of the Bureau 

 of Mines) consists essentially of a small electrically heated 

 platinum coil within a glass globe. In it a sample of dust is 

 blown up against the coil, and the pressure of the explosion, as 

 recorded by a pressure-indicator, is taken as an index of the 

 inflammability of the sample. In this case, 100 and 300-mg. 

 samples of the gas black were projected up against the coil, 

 and in spite of the fact that the coil was heated to 1200 degrees 

 C, no inflammation took place. This test cannot be regarded 

 as conclusive, for, although this apparatus has been found to be 

 very efficient in testing highly inflammable coal and other 

 dusts, it has failed to ignite a number of dusts undoubtedly 



'Published by permission of the Director of the Bureau of Mines. 

 "C. Engler, "Engineering News." volume 14. 1885. oage 299; "Abstract 

 Journal, ' Society of Chemical Industry, volume 8, page 171. 



