160 COMBUSTIBLE ACIDS. 



with distilled water, and the water evaporated to 

 dryness in a glass capsule ; the common salt 

 which remained behind weighed 2'94 grains, 

 equivalent to 1%568 grains of soda. 



In order to understand the preceding experi- 

 ment, it is necessary to know that the crystals of 

 carbonate of soda are composed of 



1 atom carbonic acid . 2'75 

 1 atom soda . . 4 



10 atoms water . . 11-25 



18 



So that 18 grains of this salt are equivalent to 4 

 grains of soda. Let us now analyze the preced- 

 ing experiment. 



(1.) We see from it that uric acid (contrary to 

 the present opinion of chemists) is capable, in 

 time, of driving off the whole of the carbonic 

 acid from carbonate of soda, and taking the place 

 of that acid. No effervescence took place when 

 the muriatic acid was poured into the residual 

 liquid from which the urate of soda had precipi- 

 tated a proof that the whole soda had united to 

 the uric acid. It appears from this, that urate 

 of soda, while in solution, has the property of 

 giving a violet colour to cudbear paper, so that 

 the acid does not destroy the alkaline qualities of 

 the soda. 



(2.) The urate of soda which remained in so- 

 lution must have consisted of 



