104 AZOTIC GAS. 



that it may not be amiss to give an equally rigid 

 proof of what it really is, drawn from the com- 

 position of nitrate of silver, a salt very frequently 

 employed in chemical analyses. 



Nitrate of silver is a white transparent salt, 

 which may be crystallized in beautiful rhom- 

 boids ; but it most commonly assumes the form 

 of thin plates, which have been compared to 

 sword blades. It contains no water of crystalli- 

 zation, though sometimes a little may be me- 

 chanically lodged between the plates of the crys- 

 tals. From this it is easily freed, by fusing it in 

 a moderate heat, and keeping it for some time 

 in that state. The small cylinders of it sold by 

 apothecaries,' under the name of lunar caustic, 

 are quite anhydrous. But I have never met 

 with them perfectly pure ; they usually contain 

 a little gold, which separates in flocks, when the 

 cylinder of nitrate of silver is dissolved ; and 

 not uncommonly, other impurities (particularly 

 nitre) are likewise present. For the experiment 

 which I am going to relate, the salt must not 

 only be anhydrous, but quite pure. 



The atomic weight of silver, as wfll be shown 

 hereafter, is 13'75, and an integrant particle of 

 oxide of silver weighs 14<'7<5. Consequently, if 

 the atomic weight of nitric acid be 6'75, as we 

 have found it to be from the analysis of nitrate 

 of lead, the constituents of nitrate of silver must 

 be 



