250 CHEMICAL DISCOVERY AND INVENTION 



new conditions have led to the practical abandonment of the 

 Brin process. 



Electrical power having become of late years more readily 

 available and cheaper, and simultaneous demands having arisen 

 for hydrogen gas, the process of submitting water to electrolysis, 

 or rather a solution of caustic potash or soda, has found some 

 considerable application. A variety of apparatus has been 

 devised with the object not only of carrying the current through 

 the liquid, but preventing local action or divergence of the 

 current, with the risk of intermixture of the oxygen and hydrogen. 

 As a fact, in the normal process small quantities of the one are 

 generally found intermixed with the other. Obviously if more 

 than a very small amount of such intermixture took place the 

 use of the gas might lead to serious explosions. 



The use of the oxyacetylene blowpipe flame for welding and 

 for cutting through metal plates has recently extended so much 

 as to lead to a greatly increased consumption of oxygen independ- 

 ently of hydrogen. The readiness with which air is now reduced 

 to the liquid state and from the liquid, both nitrogen and oxygen 

 can be separated in a condition of approximate purity, are 

 circumstances which again have led to a new position of affairs. 

 Since also nitrogen is required in such vast quantities in the 

 manufacture of cyanamide the liquefaction process has taken 

 the place of all the others in the production of oxygen for indus- 

 trial purposes. 



Before proceeding to describe the production of the gases from 

 air it will be worth while to glance at the information now 

 available as to the use of acetylene and oxygen for the purposes 

 referred to. Acetylene is a gas familiar enough for lighting 

 purposes and produced by the action of water on calcium 

 carbide. The gas is supplied for the use of engineers dissolved in 

 acetone and contained under pressure in steel bottles. When 

 burnt acetylene gives out more heat than is represented by the 

 carbon and hydrogen it contains, for it is an endothermic com- 

 pound, that is to say, in the union of carbon with hydrogen in 

 the production of acetylene, heat is absorbed. 



Hence when the carbon and hydrogen are again separated the 

 same amount of heat is evolved, and if this occurs while they 

 are both uniting with oxygen a greater amount of heat is 

 produced and a flame of higher temperature results. 



By means of an appropriate blowpipe the two gases, acetylene 



