492 Mr. De la Rue on Cochineal. 



agreeing with the formula CjgHgNgOig + 2BaO + 2HOj as 

 may be seen from the following table : — 



Theory. Experiment. 



440-28 100-00 



Nitrococcusate of Silver. — I attempted to make this salt by 

 boiling oxide of silver with an aqueous solution of nitrococ- 

 cusic acid, but there was an evident decomposition of the 

 acid, a large quantity of carbonic acid being evolved ; after 

 warming the filtered liquor a brown deposit was formed. On 

 filtering off this brown deposit a silver salt was obtained by 

 evaporation, which yielded on analysis — 



Carbon .... 23-64 

 Hydrogen . . . 1-26 

 Oxide of silver . . 38-10 



per-centage numbers not reconcilable with those of nitro- 

 coccusate of silver. 



On decomposing a hot solution of this salt with hydro- 

 chloric acid a new acid was obtained, perfectly distinct from 

 nitrococcusic acid ; it crystallized in long needles ; very in- 

 soluble in water, but soluble in aether and alcohol. 1 refrain 

 from giving any further account of this acid until the study 

 is completed. 



In order to avoid decomposition the nitrococcusate of silver 

 was prepared without the aid of heat, by dissolving carbonate 

 of silver in a cold aqueous solution of nitrococcusic acid and 

 evaporating the filtered solution in vacuo over sulphuric acid. 

 The salt crystallized in long bulky needle-like crystals of a 

 yellow colour; when dried at 100° C. the powdered salt be- 

 comes deep orange. 



It is soluble in alcohol and water, and is highly explosive 

 when heated ; in small quantities it may be decomposed by 

 a progressive heat without any violent action ; but on attempt- 

 ing to decompose a quantity amounting to -45 grm. in a 

 porcelain crucible, heated in an air-bath, the salt exploded 

 with great violence, shattering the copper air-bath and driving 

 fragments of the crucible through the copper ; the tempera- 

 ture was noted just before the explosion, the thermometer 

 standing at 200° C. ; the silver was therefore determined as 

 chloride. 



