INFLAMMABLE GAS. " 247 



mean of a great number of trials. The following was the plan Experiments 



, . , T r X, \ and observa- 



whrch I followed. ^ uons onthein- 



(l) Before beginning each set of experiments, the inflam- flammable gas 

 mable gas was carefully examined by the method formerly de- f'O"^ P^^^- 

 scribed. 



(2) Common air was always taken as composed of 21 parts 

 of oxygen and 79 of azote. 



(3) The purity of the oxygen gas employed, was ascer- 

 tained in this manner: 20 measures of it were let up into a 

 graduated tube, and 36 measures of nitrous gas added to them. 

 The diminution of bulk was noted down, and muhij>!ied by 

 0.36842. The product was the portion of oxygen contained 

 in the 20 measures of oxygen gas employed. If th s product 

 amounted to 20, I concluded that my gas was absolutely pure ; 

 if it amounted to 10, 1 concluded that the ga> contained half its 

 bulk of azote, and so on; whatever was wanting to make up 

 the 20 being always considered as azote. The oxygen gas 

 employed was partly procured from manganese and partly 

 from hyperoxymuriate of pot-ash. It was purposely employed 

 of very different degrees of purity, in different experiments, as 

 1 wanted to ascertain the effect produced by the presence of 

 different proportions of azote during the combustion of the 

 gas. 



(4) Thirty measures of the inflammable gas were generally 

 employed. They were equal to 0.3 of a cubic inch. Each 

 measure of oxygen and air was always equal to 1- 100th part 

 of a cubic inch. 



(5) The gas and the oxygen were measured separately in 

 narrow tubers, and then let up successively into a cylindrical 

 glass tube, furnished with the requisite apparatus for passing 

 an electric spark through it. This glass tube was previously 

 filled either with water or mercury, according as the combus- 

 tion was wanted to be over water or mercury. 



(0) Immediately after the combustion, the residual gas was 

 let up into a long narrow tube, to ascertain its bulk. 



(7) It was then washed in lime-water, and the diminution of 

 its bulk noted and abscribed to the absorption of carbonic acid 



gas. "~ 



(8) In some cases, the residue, thus freed from carbonic 

 Jicid, was mixed with afesh portion of oxygen gas, returned 

 to the detonating tube, detonated a second time, the residue 



X 4- measured. 



