D. CHEMISTRY AND METALLURGY. 83 



D. CHEMISTRY AND METALLURGY. 



NEW REDUCING AGENT. 



If an aqueous solution of sulphurous acid be allowed to act 

 upon fine zinc dust, the zinc is dissolved without the devel- 

 opment of gas, the solution assuming for a time a decided 

 yellow color. This liquid now possesses the peculiarity, in a 

 very high degree, of rapidly decolorizing indigo, a fact well 

 known to chemists. Schiitzenberger, who has lately been in- 

 vestigating this subject anew, ascertained that this decolor- 

 izing of the indigo is by no means the result of oxidation, but, 

 on the contrary, is a redaction ; and this power of reduction 

 in the liquid is so extraordinarily great that it will reduce, 

 with heat, the salts of copper, silver, and mercury to their 

 metals. The liquid is not related to hydrosulphuric acid, and 

 is exceedingly unstable in its free condition; but if a concen- 

 trated solution of bisulphite of soda be allowed to act upon 

 the zinc filings, we shall obtain a soda salt of the new acid 

 which has as great an affinity for oxygen as the free acid, and 

 can therefore be kept for any length of time if completely 

 excluded from the air. 6 (7, October 5, 1871, xl., 399. 



FRIABLE GOLD COIN. 



In some instances after a piece of gold coin has been struck 

 in a mint it becomes friable and crumbling. It has been as- 

 certained that this property is due to the presence of a very 

 small quantity (hardly a thousandth part) of certain metals, 

 among which lead is the most injurious. By an improved 

 process, however, this difficulty has lately been overcome. 

 This consists in passing a current of gaseous chlorine over 

 the melted metal, which is covered with borax in the ordi- 

 nary way. A chloride of gold would not be formed at this 

 high temperature, but, on the contrary, would be decomposed, 

 while the other metals unite with the chlorine so as to quick- 

 ly purify the mass. Any silver which may happen to be pres- 

 ent is not lost, as it becomes dissolved in the borax, which 

 serves as a cover for the molten gold. 3^?, March 7, 1872, 

 394. 



