^n 



<@K METjiLTLlC imoSPH'UKEYS, 



The propor- 

 tions of the 

 precipitant im- 

 portant. 



Sulphnret of 

 potash analo- 

 gous m its 

 action. 



FulmiHaiing 



Alkaline solsi- 

 tion of lead 

 precipitated 

 iuelaliic. 



State, and coaseqiieatly decompose nitric acid ; as tii<JSfc 

 formed in soliitioas of silver, mercury, copper, andT ins- 

 math. I believe however, that beside the two phesphurets 

 of oxides I have mentioned, others might be produced bj 

 repeatiag our trials, and varying the proportions of phos* 

 phoras and alkali, for these are of the greatest importance 

 in preparing the two species I have mentioned. If, for in- 

 stance, the precipitant contain too much phosphorus, or 

 too much alkali, the precipitate will be white, both from 

 the nitrate of lead, and from the nitromuriate of antimony : 

 and we cannot obtain the orange precipitate in the first case, 

 or the brown in the other, but by adding to the alcohol 

 whichever of the two substances is deficient. 



The action of sulphuret of potash exhibits a striking 

 a-nalogy with this. This sulphuret precipitates the nitrate 

 of lead red; but, if it contain too much alkali, the preci- 

 pitate is wJdte^ and if the sulphuret be s«fficientlyhidrogu- 

 retted, it is black. In the latter case however the precipi- 

 tate may be made red by adding an excess of acid to the metal- 

 lic solution, for this extricates th^ hidroguretted sulphuret. 



§ 8. Mercury dissolved in nitric acid furnishes with the 

 alcaline phosphuretted alcohol* a precipitate, that fulmi- 

 nates loudly when struck. As we do not always sncceed in 

 obtaining it equally fulminating iii this way, it appears to 

 me a more certain method, to pxe[)are it by mixing phos- 

 phuret of mercury, obtained hy means of phosphuretted 

 alcohol (see § 2), with small dry crystals of nitrate of 

 mercury. 



§ .9. Though lead dissolved in acids is not separated in 

 the metallic state hy alcohol impregnated with phosphorus f , 

 it is v/hen its oxide is held in solution by alkalis. We have 

 only to let fall a few drops of this precipitate into an alka- 

 line plumbate, when the metal and the phosphorus will im- 

 mediately unite, and separate in the form of small, black, 

 brilliant, granular crystals. The presence of the alkali in 



* That must be employed, which gives an orange or red preci- 

 pitate with solutions of lead; and it is essential, that the precipitate 

 be washed only with cold water. 



t This alcohol must not be confounded with tliat which contains, 

 Jeside phosphorus, alkali likewise. 



tJiij 



