6 ANALYSIS OF 



lofl any weight ; whereas, if it had imbibed the air that had 

 diiapptared, or the water, of which, as 1 have fiiewn, the 

 air principally confifts (as it would have done if it had 

 been melted in the procefs) it ought to have gained 4.2 

 grains. 



There was not, however, the fame certainty in the ex- 

 periments with the needles, and ftill lefs with the iron, 

 as in thofe with the bones. They generally gained a little 

 weight, and diminillied the air more than the bones. 

 The reafon of this uncertainty might be that they were 

 fometimes heated too much ; and fometimes fine fcales 

 were thrown from them, which were indeed fometimes 

 vifible when, in floating about within the velTel, they 

 crofled the fun beams, and both in the experiments with 

 the needles and thofe with the bones a vapour vifibly rofe 

 from them. When the needles were heated over lime 

 water, a thick cruft was formed upon it ; but there was not 

 fuch a precipitation of the lime as in the experiments with 

 the bones. 



That the phlogiftication of nitrous acid is owing, in 

 fome cafes, to its imbibing fomething, and not always to its 

 partifig with any thing, which the antiphlogiflians main- 

 tain is evident from its becoming phlogifticated by im- 

 bibing nitrous air. This I have obferved that it does 

 with the greateft rapidity, leaving in fome cafes not more 

 than one 1 8th part of the original quantity. M. Fourcroy 

 fuppofes ( Philofophie Chymique, p. 76) that the converfion 

 of the common nitrous acid into the phlogifticated is 

 always occafioned by its parting with oxygen. That 

 this is fometimes the cafe I have demonftrated in my ex- 

 periments with heating it in long glafs tubes ; but in the 

 prefent cafe it is not poffible that the acid Ihould have 

 parted with any thing, and leaft of all with oxygen^ fmce 

 the fmall refiduum of nitrous air is pure azote. I fliall 

 here obferve, what I did not before, that the abforption 



of 



