Jtiquiry info the Laws of Afflmi-j'. t^ 



out reduflton. But we perceive that in this fublimate the mercury cannot ^ as much 

 oxided as in the fublimation of the precipitates by the fixed alkalis or lime, becaufe it has loft 

 a part of its oxigen by the decompofition of the ammonia. The liquid which covered the 

 cipitate contained a combination of oxide of mercury, of muriatic acid, and ammonia. 



The precipitation by ammonia prefented the fame phenomena, except the effervefcence. 



8. By direfting our attention to the other metallic folutions and precipitations, the cha- 

 rafter of thofe of mercury are ^afily difcovered, as well as the modifications which de- 

 pend on the particular afFeftions of each oxide ; I therefore think we are juftified in dating 

 the following principles : 



1. The acids a£l upon the metallic oxides the fame as upon the other fubftances, in 

 proportion to their mafs, fince when a metal has become but little foluble or Infoluble, It 

 may be diflblved by an excefs of acid, or may form, by means of fuch excefs, a more du- 

 rable com}}Ination. 



2. When a metallic combination Is decompofed, the alkali or alkaline earth made ufe of, 

 produces a divifion of the acid, In proportion to the energy of its aflion. If the metallic 

 combination Is weak, water is fufficient to decompofe it ; falls with either the maximum 

 or minimum of acid are then formed. In this cafe the metallic oxides follow the fame 

 laws as other fubftances ; but it fometlmes happens that It Is not the alkaline bafe which is 

 added that aflumes Its fhare of the acid, but It is the metallic oxide on the contrary that 

 divides the precipitate with the acid ; as when we form fulminating gold, or the orate of 

 ammonia. Sometimes alfo the precipitant, the acid, and the metallic oxide from two 

 complex combinations ; one of which is Infoluble and the other remains liquid, as we have 

 feen in the decompofition of the corrofive mercurial muriate by ammonia, and in the ex- 

 periments that I have defcribed (firft feries, Nos. X. and XI.) 



In general, but particularly with rcfpecb to the metallic folutions, we muft not feparate 

 in our reafonlngs, the fubftance employed by the name of precipitant from the liquid ia 

 which the precipitation is effefted ; but attention ought to be paid equally to all the fub- 

 ftances prefented, and which may form new combinations. 



3. The coloured oxides may produce colourlefs combinations ; but on giving out a part 

 of the acid with which they were combined, their colour will again appear in proportion 

 to the quantity of acid they have yielded ; fo that this colour Is an indication of the confti- 

 tution thus eftabliftied, provided the ftate of oxidation has not been changed by any parti- 

 cular circumftance. 



4. The metallic oxides cannot be compared together, unlefs they are taken in a deter- 

 minate ftate of oxidation. All the combinations they are capable of forming vary, not only 

 from this caufe, but alfo from the proportion of acid they retain, when this proportion is 

 not determined by a cryftallization. With refpe£t to oxidation there are only two extremes; 

 that of the fmalleft, and tl^at of tJae greateft oxigcnation which can be confidered as 

 conftant. 



Vol- v.— August 1891. Bb Hencfi 



