ON THE AFFINITY OF BODIES 257 



though this was really the case. This white matter in 

 the solution of lead is nothing but calx of lead saturated 

 with fixed air ; that is to say, real white lead. If this 

 superfluous calx is separated from the solution, the com- 

 pound of lead and vinegar will immediately crystallise ; 

 and this may be effected by the addition of gum-arabic, 

 or by adding more vinegar, in order to dissolve the abundant 

 calx of lead. Fixed air is seldom necessary to bring the 

 difficultly crystallisable salt to shoot. Too much is 

 attributed to this mild acid ; and I cannot agree with 

 the author in thinking that the explosion of gold is 

 owing to it. 



P. 286. It would be difficult to show that all the 

 fixed air obtained by Mr. Lavoisier came from the minium. 

 Part, indeed, does ; but as we know T that charcoal consists 

 of phlogiston and aerial acid or fixed air, to abide by the 

 author's appellation, I ask, What becomes of that fixed 

 air which those particles of the charcoal that part with 

 their phlogiston to the lead, yield ? Recent minium gives 

 out much fixed air when it is distilled with charcoal. 



P. 193. When speaking of tartar, Mr. W. mentions 

 an inflammable earth, which is separated on saturating 

 tartar with alkali. But the tartar contains some calcareous 

 earth, which, with the acid of tartar, constitutes a salt very 

 difficult of solution ; on which account it falls to the 

 bottom. Acid of tartar contains much oily matter, where- 

 fore a compound of that acid and lime must burn. 



P. 297. We obtain caustic alkali, and not a neutral salt, 

 as the author affirms ; for the latter is obtained only when 

 chalk is boiled with tartar; in which case it is not surpris- 

 ing that the caustic alkali should crystallise on the addition 

 of an acid. 



P. 366. It is said that fixed air is the cause of the 

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