[-3*1 J' 



L. Refearches ref peeling the Lazvs of Affinity, By 

 C. Berthollkt, Member of. the French National 

 lnjlitute. 



[Continued from p. 20S.] 



i. IN 



On Metallic Solutions and Precipitates, 



the two preceding memoirs * I confidered chiefly 

 thofe fubftanccs which are fimple, or of which the compofi- 

 tion is not variable ; in the prefent one I mail endeavour to 

 afcertain what influence the degree of oxidation of metals 

 may have on their chemical action, and (hall compare gene- 

 rally this action with that of other fubftances, independently 

 of the properties I have already examined (Art. XIII.). 



The folutions and precipitates of mercury appear particu- 

 larly worthy of attention ; for chemifts have obferved them 

 with more care, and it is more eafy to determine their con- 

 ditions. 



2. In the Memoirs of the Academy of Sciences 1790, 

 Fourcroy has defcribed a fulphate of mercury analogous to 

 calomel, that is to fay, formed by mercury little oxvgenated; 

 and has fhown that the fulphate of mercury, particularly 

 when fuch a degree of heat only is employed as not to pro- 

 duce complete deficcation of the fulphuric acid and mercury, 

 is divided by the aclion of the water into two fulphates, one 

 of which may be called oxygenated fulphate, and the other 

 mild fulphate. A Ample method of obtaining this laft com- 

 bination is to dilute, with an equal volume of water, the ful- 

 phuric acid which is treated with mercury, and to boil the 

 mixture: a little fulphureous acid is formed, and, 'in (lead of 

 oxygenated fulphate of mercury, that fulphate is obtained of 

 which the properties have been fo well iuveftigated by Four- 

 croy. In determining the conftituent parts of the mild ful- 

 phate of mercury, he fixes at 0,05 the proportion of oxygen 

 which is combined with the mercury; and fuppofes that, on 

 decompofing this fait by potafh, it is pure oxide of mercury 

 which is precipitated. But the metallic precipitates retain a 

 portion of acid which he has neglected ; I therefore believe 

 that in his experiment the proportion of oxygen ought to be 

 rather greater than that which he eftablimes. In many re- 

 cent determinations made by chemifts, this conflderation has 

 been overlooked; which renders them, in fome meafure, un- 

 certain. The mild fulphate of mercury forms a permanent 



* The article on this fubjeft. given in our Lit Number, conftituted the 

 author"* feoood memuir. — 1 - 



Vol. X. X combination, 



