i8o HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



garlic " ; if " one heats it in an open vessel, small flames 

 arise from it from time to time " (Gengembre, Mem. 

 Math. Phys., Paris Academy, 1785, X. 652). The new 

 acid, which contains less oxygen than phosphoric acid, 

 was distinguished by the French chemists in 1787 as 

 PHOSPHOROUS ACID and its salts as PHOSPHITES. 



Phosphoretted hydrogen. An inflammable compound 

 of phosphorus with hydrogen was discovered in 1783 by 

 Gengembre, whilst attempting to prepare a " liver " of 

 phosphorus by the action of alkalis upon it. The discovery 

 is described as follows : 



" I put some fixed caustic vegetable alkali to digest over 

 phosphorus; at the end of some hours, I saw a multitude 

 of minute bubbles, which adhered to the surface of the 

 phosphorus : then I exposed the whole to a heat of 35 to 

 40 degrees, to accelerate the action of the alkali. Scarcely 

 was the phosphorus melted, when there arose an unbear- 

 able odour of decayed fish, and a considerable quantity of a 

 peculiar gas, which took fire explosively of its own accord, 

 as soon as it came in contact with the air " (" Memoir on 

 a new gas obtained by the action of alkalis on Kunkel's 

 Phosphorus." Read at the Academy, May 3, 1783 ; Mem. 

 Math. Phys., 1785, X. 651-658; p. 652 ; compare CrelPs 

 Chemische Annalen, 1789, I. 450-457 ; p. 451). 



The gas liberated by the action of the alkali at lower 

 temperatures did not take fire spontaneously (loc. tit. p. 655). 

 The preparation and properties of the gas were described 

 by Dalton as follows : 



" Let an ounce or two of hydrate of lime (dry slacked 

 lime) be put into a gas bottle or retort, and then a few small 

 pieces of phosphorus, amounting to 40 or 50 grains. If the 

 materials are sufficient to fill the bottle, no precaution need 

 be used ; but if not, the bottle or retort should be previously 

 filled with azotic gas, or some gas not containing oxygen, in 

 order to prevent an explosion. The heat of a lamp is then 

 to be applied, and a gas comes which may be received 



