GASEOUS COMBUSTION AT HIGH PRESSURES. 277 



(A). Preparation and Purification of Gases. 



The gases employed in the experiments were prepared in quantities of from 25 to 

 50 litres at a time, briefly as follows : 



Hydrogen by the action of pure dilute sulphuric acid upon the electrolytic 

 "crescent" zinc (guaranteed 99'98 per cent, purity), supplied by Brunner Mond 

 and Co., Ltd. ; the gas was thoroughly washed through a series of Erlenmeyer flasks 

 containing a hot alkaline solution of potassium permanganate, which treatment 

 reduced hydrocarbon impurity to a negligible point. 



Carbon Monoxide by dropping commercial formic acid (95 per cent.) into warm 

 sulphuric acid and subsequently scrubbing the gas in a coke tower with a spray of 

 strong caustic soda solution. 



Methane* by the action of dilute hydrochloric acid upon aluminium carbide, and 

 subsequent liquefaction of the washed and dried gas in a cylindrical glass receiver 

 immersed in liquid air. The liquid hydrocarbon was finally fractionated, the first and 

 last tenths being rejected. 



Ethane* by the decomposition of zinc ethide (supplied by K.AHLBAUM) with water, 

 and subsequent liquefaction of the washed gas and fraetionation of the liquid, as in 

 the case of methane. 



Etliylene* by the interaction of ethyl alcohol and syrupy phosphoric acid, of specific 

 gravity 175, at 200 C. to 220 0. (NEWTH'S method. 'Trans. Chem. Sue.,' 1. 901, 

 vol. 79, p. 915), and subsequent liquefaction and fraetionation, as in the cases of 

 methane and ethane. 



Oxygen by gently heating recrystallised potassium permanganate and washing the 

 resulting gas with strong caustic potash solution. 



The purified gases were collected over a mixture of equal volumes of glycerine and 

 water in large glass holders each of 15 to 20 litres capacity, from whence they were 

 subsequently drawn into the cylinder of the compressing pump. 



(B). The Compression Cylinder and Pump. 



This part of the installation provides for the separate compression of each gas in 

 a steel cylinder over glycerine and water. Fig. 1 represents the cylinder, A (internal 

 capacity about 2|- litres), which was machined out of a mild steel forging and closed 

 at either end by a special type of valve. The upper valve, B, serves for the admission 

 of the gas from the holder, and is so constructed that as soon as the cylinder is full 

 of gas the holder may be shut off by a movement which simultaneously opens 

 connection with one or other of the high-pressure storage cylinders into which the 

 gas is sent after compression. The lower valve, C, is provided with fairly wide 



* The purity of the above-mentioned hydrocarbons was in each case established by a careful explosion 

 analysis with an excess of pure oxygen. 



2 o 2 



