VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 5(33 



and during the latter part of the process this air was accompanied with yellowish 

 fumes. I stopped the process when it had produced 50 oz. measures of air. 

 The receiving water, and particularly the air, had a strong but peculiar smell of 

 nitrous acid. The air was well washed with the receiving water, but was not 

 freed from the smell. The receiving water, which was 50 oz. was slightly acid, 

 and the residuum alkaline. I dissolved the latter in the former, and found the 

 mixture alkaline. 10 grs. of weak nitrous acid were added to it, which saturated 

 it, and 105 grs. of this spirit of nitre was found to contain the acid of 60 grs. 

 of nitre; therefore the JO grs. contained the acid of 5.7 grs. of nitre, which, 

 by Mr. Kirwan's experiments is equal to 2 grs. of real nitrous acid. We have 

 therefore 34 grs. weight of dephlogisticated air produced, and only 2 grs. of real 

 acid missing ; and it is not certain that this quantity was destroyed, because some 

 portion of the glass of the retort was dissolved by the nitre, and some parts of 

 the materials employed in making the glass being alkali, we may conclude that 

 the alkali of the nitre would be augmented by the alkali of that part of the glass 

 it had dissolved. As the glass cracked into small pieces on cooling, and some 

 part of the coating adhered firmly to it, the quantity of the glass that 

 was dissolved could not be ascertained. From this experiment it appears, that if 

 any of the acid of the nitre enters into the composition of the dephlogisticated 

 air, it is a very small part ; and it rather seems that the acid, or part of it, 

 unites itself so firmly to the phlogiston as to lose its attraction for water. 



13. " The vitriolic salts also yield dephlogisticated air by heat; and in these cases 

 the dephlogisticated air is always attended with a large quantity of vitriolic acid 

 air or sulphureous vapour," even when the salts used are not known to contain 

 any phlogistic matter. Mr. Scheele mentions his having obtained dephlogisti- 

 cated air from manganese dissolved in acid of phosphorus, and also from the 

 arsenical acid: whence it appears that these acids, or perhaps any acid which can 

 bear a red heat, can concur to the production of dephlogisticated air. It is 

 necessary to remark, that no experiments have been yet published showing that 

 dephlogisticated air can be produced from salts formed by the muriatic acid. 

 The acids which produce salts suitable for this purpose have all a strong affinity 

 with phlogiston; and the marine acid has either a very small affinity with it, or 

 else is already saturated with it, at least so far saturated as not to be able to attract 

 it from the humour. 



14. " The dephlogisticated air obtained from the pure calces of metals may 

 be attributed to the calces themselves, attracting the phlogiston from water which 

 they have imbibed from the atmosphere, or from their dephlogisticating the fixed 

 air which they are known to contain." It is very probable, that the dephlogis- 

 ticated air extruded from growing vegetables may be owing to their dephlogis- 

 ticating the water they grow in ; but it appears most probable that the plants 



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