254 Memoir on the Quantity of 



proof by Sulphuret, 



The proof by fulphuret is that beft calculated to afcertain 

 the quantity of vital air contained in any gafeous fluid, fince 

 it will leave the mephitic air, and the other kinds of air which 

 do not combine with it, without fear of any other gafeous 

 fuhflancc being produced, or any loft, except the quantity of 

 vital air, which alone has an affinity with the fulphuret, as 

 I aflTured, myfelf in 1787. A hundred parts of atmofpheric 

 air expofed to fulphuret loft between O'^i and 0*23 ; and as 

 feveral other prvjofs on ihe fame air, made with nitrous gas, 

 had taught me that it experienced no feniible variation, I 

 was then convinced that the air which we breathe in Cata- 

 lonia is conftantly compofed of irom o*2i to 0*23 of vital air, 

 and from 077 to 079 of azotic gas. To afcertain whether 

 there might not be variations afterwards in the proportion of 

 thefe two principles which conftitute in the atmofphere that 

 elaftic fubftance on which our life chiefly depends, I contw 

 nued mv experiments by means of fulphuret. 



In order to Ihorten the operation, I provided fome glafs 

 fiafks of diflerent fizes, each ending in a narrow neck, and 

 furniflied with a ground ftopper. I filled one of them with 

 liquid fulphuret of lime, and, having immerfed the neck of 

 It in water, I introduced into it, with the utmoft fpeed, 

 through its orifice, a portion of atmofpheric air. The fiafk 

 "being then flopped was fhaken for a little time, and on exa- 

 mining it immediately I found its diminution complete. My 

 refcarches were foon after dire<Slcd towards deicrminins^ the 

 refpeclive quantities of air neceffary to be introduced to that 

 of the fulphuret, not only that I might learn the fliorteft pof- 

 iible means of being able to effect my proofs, but alfo to 

 afcertain whether they would be equally correal if made with 

 a large (ir a fmalt portion of vital air. Different experiments 

 made with this view furniflied me with the following obfer- 

 valions : 



A quantity of atmofpheric air, from a fourth part of a 

 meafure to a whole one, which is the volume of an ounce of 

 water, loft between 0'2i a.nd 0-23, in flafks capable of con- 

 taining from one and a half to fix meafiires, filled with liquid 



fulphuret, 



