442 MEANS OF ASCERTAINING THE QUALITY OF GLASS. 



pruBsic acid is perceived the first rnoment of the mixture, 



bat I never could discover any traces of it. 



Decomposed Nitric acid decomposes it by the help of a bailing heat ; 



y nitric aci ; ^^^ ^^^ products are nitrate of silver, and nitrate ot ammonia, 



if it be continued long enough. 



sulphuretted It is decomposed by sulphuretted hidro^en ; the ammonia 



*= ' and vegetable matter remaining in the liquor. 



and potash. Caustic potash decomposes it ; black oxide of silver being 



separated, and ammonia di sen ganged. 



Ammonia dis- It is soluble in ammonia; but by a slow evaporation it 

 solves It with- . ... . . 



out alteraiion. may be separated from it, retaining its original colour and 



other properties, particularly that of detonating by heat, and 

 not by simple contact. 

 A virulent poi- Its most important property to be considered, with respect 

 to the use made of it, is its action on the animal econom}'. 

 Mr. Pajot-la-Foret, who has made a great many experiments 

 on this subject, has found, that very small doses are suffi- 

 cient to destroy pretty strong animals, as cats. They all 

 expired in the most dreadful convulsions. It is unquestion- 

 ably one of the most violent poisons to be found among me- 

 tallic compounds. 



XVI. 



Memoir on the Means of forming a Judgment of the Quality 



" of Glass, particular Ii/ Window Glass, and distinguishing 



such as is liable to alteration: by Mr, Guyton. Read at 



the General Meeting of the Society of Encouragement, 



March the Uth, 1807*. 



son 



Prize proposed ABOUT two years ago Mr. Guyton suggested to the 

 for a test of societj^ to propose as the subject of a prize, a ready method 

 good glass. of ascertaining the goodness of window glass. It appears,; 



that, from the negligence or ignorance of the glass maiiufac- 

 Frenchwin- t^rers, tlie windows in several large houses had become dis- 

 dow glass liable figured in a few months by a spontaneous alteration of the 

 ^ ^P°'** glass, which destroys its transparency : accordingly it \^as of 



some importance, to be able to guard against this inconve- 

 Jhe question jiience. The prize was proposed, and its term prolonged; 



• Abridged from Anaales de Chimie, vol. Ixii, p. 5, April, 1807 



but 



