210 Analysis of the Chinese Gong. [Sept. 



The analysis of bell-metal is so simple, and so well known, 

 that it may seem superfluous to enter into details; but as such 

 details are the only means of detecting the mistakes into which 

 the experimentor may fall, I think they ought never to be neg- 

 lected. 



101*85 grains of the gong were put into a glass phial, and 

 two ounces of moderately strong nitric acid poured over it. The 

 acid speedily became green, an effervescence took place, and a 

 white powder appeared. When the action of the acid appeared 

 at art end, it was decanted off, and two ounces more of the same 

 acid substituted in its place. The whole copper was dissolved by 

 this last portion, and a white powder remained at the bottom of 

 the phial. The acid solution was decanted off, and the white 

 powder carefully washed with distilled water. 



The acid solution was evaporated to a small quantity, to get 

 rid of the excess of acid. During the evaporation a portion of 

 white powder precipitated. It was separated by the filter, and 

 mixed with the first portion. The white powder thus obtained 

 was dried in the open air. It acquired, when dry, a tinge of 

 green. Conceiving that this might be owing to the presence of 

 copper, I digested it for a week in nitric acid' but no copper was 

 taken up. It was then dried, and exposed to a red heat. In that 

 stat« it was yellow, and wqighed 25*36 grains. Now this yellow 

 powder was peroxide of tin, which is a compound of 1 atom tin 

 and 4 atoms oxygen, or of 14*705 tin + 4 oxygen: and 14*705 

 : 4> :: 25*36 — x : x = 5*423. Hence the quantity of tin in 

 the oxide was 19*937; but the quantity of gong analysed -was 

 101*85 grains: 100 grains, therefore, contain 19*573 grains of 

 tin. This approaching so near 20, 1 have supposed that +th was 

 the proportion of tin intended to be mixed with the copper. 



The nitric acid solution was evaporated to dryness, redissolved 

 in water, and tried for silver by nitrate of silver, and for lead by- 

 sulphate of soda. No precipitate appeared in either case. Hence 

 I consider myself entitled to regard the gong as free from both 

 silver and lead. To see whether any zinc was present, the nitrate 

 was mixed with as much sulphuric acid as was sufficient to satu- 

 rate the copper. It was then evaporated to dryness, redissolved 

 in water, and set asidefor spontaneous crystallization. Regular 

 crystals of sulphate of copper were obtained to the very last drop. 

 Hence no zinc was present. The gong, by my trials, was an 

 alloy of 



Copper 80*427 



Tin . 19*573 



100*000 



