348 Journal of the Asiatic Society of Bengal. [June, 1908. | 
the alkaline tartarate solution is gradually added until the pre- 
cipitate of copper hydrate first formed is just re-dissolved. 
Excess of the alkaline solution is to be avoided. Strong formalde- 
hyde is then added until the solution smells perceptibly of the 
reagent. The solution is tilted to one side and heat is applied to 
High temperature is essentially necessary, and in fact the mixed 
solution was kept in boiling water without any perceptible 
deposition of copper. Formaldehyde vapour was passed over hot 
Fehling’s Solution without mue success, bee 
_Grape-sugar and milk-sugar were substituted for formalde- 
hyde, but in these cases red cuprous oxide was, as is well known, 
seraped off, dried, dissolved in nitric acid, precipitated and 
weighed as oxide. The percentage of copper was found to be 
98°6. The copper was slightly blackened in the course of 
drying 
hydrate in excess of ammonia, and says that the formation of 
ed. : 
Tt has always puzzled chemists to ascertain the conditions 
which determine the deposition of silver sometimes as a fine y- 
divided powder and sometimes as a shinin, irror. oge 
a 
pointed out, hardly applicable, and specially so in the present 
investigation, as the deposition is not the result of a complete 
ti F oS ai Ne oe 


