PioduB obtained b^ Coinhiijlim of the Di.iW!»id. i^^ 



came over was produced by the decompofitioii of the nitre, and contained fo little fixed air 

 as to occafion only a very flight precipitation from lime-water. After the tube had grown 

 cold, the alkaline matter contained in it was diirdved in water, and the whole of the dia- 

 monds were found to have been deftroyed- As an acid would difengage nitrous air from 

 this folution as well as the fixed air< the quantity of the latter could not in that manner 

 be accurately determined. To obviate this inconvenience, the fixed air was made to unite 

 with calcareous earth by pouring into the alkaline folution a fulEci "nt quantity of a faturated 

 folution of marble in marine acid. The veffel which contained them, being clofed, was left 

 undiilurbed till the precipitate had fallen to the bottom ; the folution having been previoufly 

 heated, that it might fubfide more perfeftly. The clear liquor, being found by means of 

 lime-water to be quite free from fixed air, was carefully poured off from the calcareous 

 precipitate "*. The veflel which was ufed on this occafion was .a glafs globe, having a tube 

 annexed to it, that the quantity of the fixed air might be more accurately meafured. After 

 as much quickfilver had been poured into the glafs globs containing the calcareous precipi- 

 tate as was neceffary to fill it, it was inverted in a veffel of the fame fluid. Some marine 

 acid being then made to pafs up into it, the fixed air was expelled from the calcareous 

 earth, and in this experiment, in which two grains and a half of diamonds had been em- 

 ployed, occupied the fpace of a little more than lo.i ounces of water. 



The temperature of the room when the air was meafured was at 55°, and the barometer 

 ftood at about 29.8 inches. 



From another experiment made in a fimilar manner with one grain and a half of dia- 

 monds, the air which was obtained occupied the fpace of 6.18 ounces of water; according 

 to which proportion, the bulk of the fixed air from two grains and a half would have been 

 equal to 10.3 ounces. 



The quantity of fixed air which was thus produced by the diamond does not differ much 

 from that which, according to M. Lavoifier, might be obtained from an equal weight of 

 charcoal. In the Memoirs of the French Academy of Sciences for the year 1 781, he has 

 related the various experiments which he made to afcertain the proportion of charcoal and 

 oxigene in fixed air. From thofe vi'hich he confidered as mofl; accurate, he concluded 

 that 100 parts of fixed air contain nearly 28 parts of charcoal and 72 of oxigene. He efti- 

 mates the weight of a cubic inch of fixed air, under the preflure and in the temperature 

 abovementioned, to be .695 parts of a grain. If we reduce the French weights and meafures 

 to Englifii, and then compute how much fixed air, according to this proportion, two grains 

 and a half of charcoal would produce, we (hall find that it ought to occupy very nearly the 

 bulk of 10 ounces of water. 



M. Lavoifier feems to have thought tliat the aerial fluid produced by the combuftion of 

 the diamond was not fo folubla in water as that produced from calcareous fubftances. 

 From its refemblance, however, in various properties, hardly any doubt could remain that it 

 confifted of the fame ingredients; and 1 found, upon combining it with lime, and expofing 

 it to heat with phofphorus, that it afforded charcoal in the fame manner as any other cal- 

 •areous fubllance. 



• If much water had remained, 3 confiderabic portion of the fixed air would h.ive been abforbed by it. But 

 by ihc fame meihod as that dcfcribcl abuvc, 1 obfervcd that as much fixed air miglit be obtained from a folu- 

 lian of mineral alkali, at by adding an acitl to an equal quantity of the fame kind of alkali. T. 



A a 2 XII. U/eful 



