22 Sketch of the latest Improvements [J as. 



sulphur. If we suppose it a compound of one atom metal + two 

 atoms sulphur, then an atom of antimony will weigh 11*249. 



V. Re-agents. 



I shall state under this head the result of some experiments 

 undertaken by different persons to determine the best re-agents for 

 detecting the presence of different bodies in solution. 



1 . Mercury. — Professor Pfaff, of Kiel, has made a set of expe- 

 riments on the best means of detecting mercury in solution, espe- 

 cially when in the state of corrosive sublimate. The following are 

 the general conclusions which he considers liimself as warranted to 

 draw from these experiments : — 



The experiments hitherto made on the action of sulphureted 

 hydrogen on solutions of mercury, are in contradiction with each 

 other, and of course insufficient to answer the purpose for which 

 they were intended. 



VVater impregnated with sulphureted hydrogen is the most deli- 

 cate test of the presence of corrosive sublimate and pernitrate of 

 mercury ; for it discovers these salts, though diluted with 40,000 

 times their bulk of water, and tliough they do not exceed the 

 quantity of -ig- or -pi-^ part of a grain. 



The action of this liquid upon solutions of mercury Is distin- 

 guished from its action on all other metals by this circumstance — if 

 there be present in the solution any peroxide of mercury, the preci- 

 pitate, which is at first in brownish or blackish flocks, becomes very 

 speedily vvliite. The addition of the smallest quantity of peroxide 

 of mercury will render the black precipitate white, provided it be 

 agitated. 



Protoxide of mercury in all cases produces a black precipitate 

 with sulphureted hydrogen. 



If a small piece of copper coin be put into the solution suspected 

 to contain mercury, it will be covered with a white coating, or at 

 least with white streaks ; which, when rubbed, acquire the metallic 

 lustre. By this method Mr. Pfaff was able to detect the presence 

 of ^V of a grain of corrosive sublimate when dissolved in 20,000 

 times its weight of water. 



2. Murmtic Acid. — Mr. Meyer, of Stettin, has made some 

 curious observations on the delicacy of nitrate of silver, pronitrate 

 of mercury', pernitrate of mercury, and the solution of subperni- 

 trate of mercury in water, as tests for the discovery of muriatic 

 acid. He found nitrate of silver the most delicate of these four 

 salts. It detected one part of muriatic acid dissolved (in the state 

 of common salt) in 1 13,064,000 parts of water ; but upon this very 

 dilute solution the other three salts had no eftect. A solution of 

 one part acid in 56,832,000 parts of water was not aflccted by the 

 mercurial salts. A solution of one part muriatic acid in 28,416,000 

 parts of water was rendered slightly opalescent by the pronitrate of 

 mercury, but not altered by the two other mercurial salts. A 

 solution of one part of muriatic acid in 14,208,000 parts of water 



