VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. Gq5 



solving metals; and the other, describing some curious appearances which occur 

 in the precipitation of silver from its solution in nitrous acid by iron, and by 

 some other substances. In a subsequent paper I hope to continue the subject of 

 metallic dissolution* and precipitation, first, by adding some experiments on the 

 quantities and kinds of gas produced by dissolving different metals in different 

 acids, under various circumstances ; 2dly, by submitting certain general proposi- 

 tions, which seem deducible from the facts related; and lastly, by concluding 

 with some reflections relative to the theory of metallic dissolution and precipitation. 



Part 1. On the ejects of compounding the vitriolic and nitrous acids, under 

 various circumstances, on the dissolution of metals. 



§ 1. On the mixture of oil of vitriol and nitre. — 1. The properties of the 

 several acids, in their separate states, have been investigated with considerable 

 industry and success; and those of one compound, aqua regis, are well known, 

 on account of its frequent use in dissolving gold: yet not only various other com- 

 binations of different acids remain to be examined; but also the changes of pro- 

 perties to which these mixed acids are subject, from the difference of circum- 

 stances, especially those of concentration, temperature, and of that quality 

 which is called, properly or improperly, phlogistication, are subjects still open for 

 inquiry. 



2. As I shall have frequent occasion to speak of the phlogistication and dephlo- 

 gistication of acids, I wish to premise, that by these terms I mean only certain 

 states or qualities of those bodies, but without any theoretical reference. Thus 

 vitriolic acid may be said to be phlogisticated by addition of sulphur or other in- 

 flammable matter, by which it is converted into sulphureous acid, without deter- 

 mining whether this change be caused by the addition of the supposed principle 

 phlogiston, as one set of philosophers believe, or by the action of the added in- 

 flammable substance in drawing from the acid a portion of its aerial principle, 

 by which the sulphur, its other element, is made to predominate, as others have 

 lately maintained. It were much to be wished that we had words totally uncon- 

 nected with theory; that chemists, who differ from each other in some specula- 

 tive points, may yet speak the same language, and may relate their facts and ob- 

 servations, without having our attention continually drawn aside from these, to 

 the different modes of explanation which have been imagined. But at present 



* The English word solution has two significations in chemistry ; one, expressive of the act of dis- 

 solving, as when we say, that *' solution is a chemical operation;" and the other, denoting the sub- 

 stance dissolved in its solvent, as " a solution of silver in nitrous acid," The French language is 

 equally equivocal, as the word " dissolution" is used in both the above-mentioned senses. In treating 

 on this subject, in which both meanings were very frequently required, sometimes in the same sen- 

 tence, I could not but be sensible of confusion in the stile, and I have therefore confined the word 

 solution to express the substance dissolved together with its solvent, and the word dissolution to denote 

 the act of dissolving.— Orig. 



