C hap. 38.] Combuftion of Phofybarus. 249 



downy mafs. This concrete acid has fo ftrong an at- 

 traction for water as to imbibe it from the atmofphere 

 with aftonifning rapidity, till it is converted into a li- 

 quid confiderably more denfe, and of greater fpecific 

 gravity than water. 



From the experiments detailed in M. Lavoifier's 

 elementary work on chemiftry, it appears that one 

 pound of phofphorus requires one pound eight ounces 

 of oxygen gas for its combuftion, and that two pounds 

 eight ounces of concrete pholphoric acid are pro- 

 duced. 



The phofphoric acid may be obtained by three 

 Other proceffcs befides this. If phofphorus is melted 

 in hot water, and a ftream of vital air pafTed through 

 it, it becomes oxygenated. The fame thing happens 

 by plunging it in nitrous acid, from which it abftracts 

 the oxygen. It may be alfo acidified by fimple expo- 

 fure to the atmofphere, which ought not at the time 

 to exceed the temperature of fixty degrees, from the 

 danger of inflammation ; in this (ituation, by a gradual 

 combuftion, it attracts the oxygen of the atmofphere, 

 and becomes converted into an acid. 



The cauftic fixed alkalies difiblve phofphorus by 

 the affiftance of heat. During this combination a 

 fetid gas is difengaged, which has the fingular property 

 of exploding as foon as it comes in contact with at- 

 mofpherical air, and ftill more rapidly by contact with 

 vital air. 



The phofphoric acid forms peculiar falts with, the 

 alkalies and fome of the earths, and has the property 

 of corroding glafs. With the mineral alkali it forms 

 a fait, the tafte of which is lefs unpleafant than that of 

 other neutral falts, and which is well calculated to an- 

 fwer the purpofes for which neutral .falts are ufed in 

 medicine. . The phofphoric acid acts only on a fmall 



number 



