220 



METTALLOIDS. 



is contained in the gas. In order that the gas may be 

 safely evolved, it is best to heat the vial in a tea-cup 

 containing salt, dissolved in three times its bulk of 

 water. The addition of salt has the effect of raising 

 the boiling point. The comparatively high tempera- 

 ture required, may thus be obtained without exposure 

 of the vial to the direct flame of a lamp. 

 Explain the 546. EXPLANATION. In the action which 

 above process, occurs in making phosphuretted hydrogen 

 from potash, water, and phosphorus, the latter plays 

 the part of an extremely rapacious element. It makes 

 no distinction in the objects of its appetite, but seizes 

 upon both oxygen and hydrogen of the water, two 

 substances as widely different from each other as pos- 

 sible. It forms with the one, phosphuretted hydrogen, 

 and with the other, what might be called phosphuret- 

 ted oxygen, but is, in fact, an acid. Potash is em- 

 ployed in the process, to promote the formation of this 

 acid. In its absence, water resists the affinities of the 

 phosphorus, and neither acid or phosphuretted hydro- 

 gen are obtained. 



COMPOUNDS OF HYDROGEN WITH CARBON. 



547. Most of the compounds of carbon and hydro- 

 gen belong to the vegetable world, and will therefore 

 be more properly considered in the chapter on organic 

 chemistry. Only two of them, which exist ready 

 formed in nature, will be here mentioned. 



