TRANSACTIONS OF THE SECTIONS. 29 



converted into an oxychloride, which by giving up its oxygen to the sulphur combined 

 with the silver, leaves this in a metallic state and free to amalgamate with the mercury. 

 This is proved by boiling native sulphuret of silver with oxychloride of copper * in a 

 solution of common salt, when metallic silver will be obtained ; or as a more practical 

 experiment, by mixing some ricii ore with these materials and mercury at the ordinary 

 temperature ; in about an hour the whole of the silver will have become amalgamated, 

 when on separating all the soluble salts by filtration, and the addition of chloride of 

 barium, sulphate of barytes will be precipitated, equivalent in quantity to that of the 

 sulphur which has been acidified ; it will thus be made evident that the sulphuric acid 

 can only have been formed by the decomposition of the sulphuret of silver, and could 

 not have existed if this metal had become combined with chlorine, according to the 

 theory hitherto received. 



The action of oxychloride of copper in the reduction of silver ores seems to be con- 

 tinuous, and its theory thus offers some analogy to that of the manufacture of sulphuric 

 acid : by giving up its oxygen to the sulphur previously combined with the silver, the 

 oxychloride of copper is converted into a protochloride ; and this into a bichloride, by 

 the action of the chlorine, which is evolved by the decomposition of the salt when at- 

 tacked by the sulphuric acid that has been formed. This bichloride is again decom- 

 posed by the mercury, and first a proto- and then an oxychloride of copper are formed : 

 the sulphur of the silver becomes acidified, and the action is continued in the same 

 manner until the whole of the metal is amalgamated. 



By the direct use of oxychloride of copper, instead of forming it in the " tortas " by 

 means of the sulphate, as in the usual method, the author has obtained very advanta- 

 geous results, not only as far as regards a great saving of time, labour and materials, 

 but also by the extraction of a much larger quantity of silver than could possibly be 

 got out by the old process. 



The loss of mercury, although greatly diminished by its means, cannot indeed be 

 entirely avoided, as is evident from the theory of the operation ; but the principal ad- 

 vantage derived from this method consists in the larger amount of silver produced; and 

 this is a very important point to be considered, when on a moderate calculation at 

 least the value of half a million sterling per annum is left in the ore, and thus irretrie- 

 vably lost, in Mexico alone, through the imperfections of the usual process of amalgama- 

 tion. In order to protect entirely the mercury from being attacked, it would be ne- 

 cessary to have in contact with it some metal more readily oxidizable, as zinc, tin, or 

 lead ; but any of these bodies would decompose the oxychloride of copper, and thus 

 destroy its action on sulphuret of silver ; perhaps a very weak solution of carbonate 

 of soda or potash would not have this effect, and would serve to neutralize the acid 

 that is disengaged. 



The author then treats of the proper mode of forming the oxychloride of copper to 

 be employed in the reduction of silver ores; points out the practical good effects which 

 have resulted by application of his theoretical views, and shows the importance of a 

 full consideration of the subject by statements of the great loss of silver which is ex- 

 perienced by following the old routine, unaided by science. 



At Guenaxato this loss is estimated at 10 per cent. ; Fresmetto, 28 ; Zacatecas, 

 35 to 40 ; nor is this the extreme case. 



On Mr. Phillips's Method of discovering Adulteration in Tobacco. 

 By Joseph Bateman, LL.D,, F.R.A.S. 



The basis of this plan is the ascertainment and comparison of the relative propor- 

 tions of soluble and insoluble matter in tobacco ; water being the solvent. Numerous 

 experiments have proved that every kind of vegetable matter has a determinate por- 

 tion, which is soluble in water; thus rhubarb-leaves range from 18 to 26 per cent., 

 and horse-radish, lettuce, oak, elm, and many others, have their definite limits. This 

 amount, with reference to tobacco, in no case exceeds 55 per cent, of the tobacco : and 

 thus if tobacco be adulterated with matter soluble in water, the extractive or soluble 

 part is increased, whilst the ligneous and insoluble matter are correspondingly de- 



* This oxychloride of copper must be partially soluble in a solution of salt, as that prepared 

 in the common way would have no effect. 



