M. Deville on certain Phenomena of Diffusion. 61 



easier to prepare, and it can be kept for a long time without 

 undergoing any change. 



The new powder contains chlorate of potash ; and this, in all 

 substitutes for gunpowder of which it is a constituent, forms 

 products of combustion at a high temperature, which attack the 

 firearms. If the decomposition of the white powder takes place 

 in accordance with the equation already given, it is not easy to 

 see why this evil is to be feared. It could be most simply de- 

 cided by firing off a certain number of shots with a given weapon. 

 Another advantage of the new powder is its difficult explosibility 

 by pressure and percussion. Explosion is only produced by the 

 heaviest blow of iron upon iron ; it is not produced by the fric- 

 tion of wood upon metal, or between stones, &c. The new pow- 

 der is also far easier of preparation than the old ; and if the raw 

 materials are at hand, a large quantity of it may be prepared in 

 a few hours with no other apparatus than a stamping-mill and 

 mixing tub. 



The following observations have been made by Ste.-Claire 

 Deville* on the influence exerted by the sides of certain vessels 

 on the motion and composition of gases traversing them. 



In laboratories, earthen and stoneware vessels are often used 

 for reaction with gases at a high temperature. They are suit- 

 able for most gases ; but they are permeable to hydrogen, and 

 they absorb water. 



1. A rapid current from hydrogen is passed through one of 

 these tubes. The tube is closed by two corks, in which are fitted 

 glass tubes ; one of these tubes admits hydrogen ; the other, 

 which dips in water, serves for the escape of the gas. On 

 closing the stopcock by which hydrogen enters, not only does 

 the gas cease to be liberated, but the water rises to a height of 

 60 to 70 centimetres above its level, as if the hydrogen had been 

 drawn into the interior of the apparatus. With coal-gas the 

 aspiration is less, and appears to depend on the density of the 

 gas ; and there is none at all in the case of carbonic acid. 



2. If the air be passed more slowly into the interior of the 

 tube, but still more rapidly than in the majority of operations, 

 the gas collected in the trough is no longer hydrogen, but pure 

 air. 



3. If an earthen tube be made red-hot in a furnace, and a 

 current of hydrogen be passed through it, a mixture of carbonic 

 acid and nitrogen (and also sulphurous acid if the combust- 

 ible contains pyrites) is obtained — that is, the gases of combus- 

 tion by which the tube is surrounded. The experiment succeeds 



* Comptes Rendus, March 1861. 



