14 On a Comhhiation of 



all the experlinents on the combinations of oxymuriatic gas, 

 described in iny last two papers. 



The gas proclnccci by the action of muriatic acid on the 

 sails which have been called hyper-oxynniriales, on thecon- 

 irary, diflcrs verv much in its properties, according as the 

 manner in which it is prepared and collected is ditTerent, 



When much acid is employed to a small quanlitv of salt, 

 and the gas is collected over water, the v.ater becomes, 

 tinged of a lemon colour ; but the gas colltctcd is ihc same 

 as that procured from manganese. 



When the gas is collected over mercury, and is procuixd 

 from a weak acid, and from a great excess of salt, {)y a low 

 heat, its colour is a dense tint of brilliant yellow green, and 

 it possesses properties entirely difierent from the gas col- 

 lected over water. 



It son)etimes explodes during the time of its transfer from 

 one vessel to another, |)rodncing heat and light, with an 

 expansion of volume; and it tnay be alwavs made to ex- 

 plode by a very gentle heat, often by that of the hand*. 



It is a compound of oxvmuriatic gas and oxvgen, mixed 

 with some oxvnimiatio gas. This is proved by the results 

 of its spontaneous explosion. It gives off, in this process, 

 Iroin one-sixth to two-fifths its volume of oxygen, loses its 

 vivid colour, and becomes common oxymuriatic gas. 



I attempted to obtain the explosive gas in a pure form, by 

 applying heat to a solution of it in water; but in this case 

 there was a partial decomposition ; and some oxygen was 

 disengaged, and some oxymuriatic gas formed. Finding 

 that in the eases when it was most pure, it scarcely actea 

 upon mercury, I attempted to icparate the oxvmuriatic o-as 

 with which it is mixed, by agitation in a tube with this 

 metal ; corrosive sublimate formed, and an elastic fluid was 

 obtained, which was almost entirely absorbed by one-fouilh 

 of its volume of water. 



This gas in its pm-e form is so easily decomposable, that 

 it is dangerous to operate upon considerable quantities. 



In one set of experinients upon it, ajar of strong (rlass, 



* My brother, Mr. J. Davy, from whom I receive constant and able as- 

 ii'itance in all my chemical iiiqiiiiies, liad several times observed explosions, 

 in transferring tlic gas frtni hyper-o);\ muriate of potash, over mercury, 

 and he was incHncd to attribute the phxiionienon to the combustion of a 

 thin film of iiiercury, in contact with a globule of gas. ! several times en- 

 deavoured to prc-tluce I'le efl'ect, but without success, till an acid was em- 

 ployed for the prtparatioii of the gas, so diluted as not to alTord it without 

 the assistance of heat. The cliange of colour and expansion .of voluinc, 

 when the cllect look place, immediately convinced nip that it waii owing to 

 a dci;omi;oiiliun of tl;e jjas. 



containing 



