6o Mr. kir wan’s Experiments and Obfervat.ions on 
Of the precipitation oj met ah by each other from the mineral 
acids* 
I am now come to the laft point of' my inquiry, and the 
mold difficult to be let forth with that degree of precition which 
I have been enabled to attain in the former parts ; for, in the 
firft place, it is neceflary to find the quantity of phlogifton in 
each of them, not only in general, but according to their 
various degrees of dephiogiftication by each of the acids. In 
this laft particular I cannot aftert that L have attained any thing 
like a certainty, yet I hope what I advance may not be ufelefs 
to chvmical readers, as it is not altogether groundlefs, as-it con- 
tradicts no chymical fa£t, but, on- the contrary, is- agreeable, 
to many, and aifords a ready folution of all the phenomena.. 
Of the abfolute quantity of phlogifton in metals. . 
The proportion of phlogifton in metallic fubftances rela- 
tively to each other has been inveftigated in fo mafterly a man- 
ner by Mr. bergman, that T lay it down as the ground of my 
inquiries. After his difeovery all that remained was to find the 
abfolute quantity of it in any one metal, for then, by an eafy 
calculation, it may be determined in all txhe reft. The fub- 
ftance I chofe for this purpofe was regulus of arfenic, as being 
moft capable of dephlogiftication by nitrous acid, thougli 
not altogether fo. 
From ioo grs. of regulus of arfenic, diftblVed in dilute 
nitrous acid, as already feen, 102 cubic inches of- nitrous air 
and nf ths are obtained, barometer at 30°, thermometer at 6o°. 
1 muft add, that I made the experiment on 5 grs. only, fo that 
the calculation relates only to the quantity of air which 100 
grs. 
