Dr. Schunck on Rubian and its Products of Decomposition. 427 



strained through calico, and acid is added to it, which produces 

 a yellow precipitate. This is filtered, washed and dissolved in 

 boiling carbonate of potash. The solution on cooling deposits 

 crystals of rubiacate of potash, which are placed on a filter and 

 washed with cold water. From a solution of the potash salt, the 

 acid may be precipitated by muriatic or any other strong acid. 

 Some rubiacic acid prepared in this manner was analysed with 

 the following result : — 



I. 0*3160 grm. gave 0-7090 carbonic acid and 0*1010 water. 

 In 100 parts it contained, therefore, — 



Carbon 61*19 



Hydrogen 8*55 



Oxygen 35*26 



In my former experiments I obtained as a mean of three 

 determinations the following numbers : — 



Carbon 57*28 



Hydrogen ..... 2*47 



Oxygen 40*25 



I was at first unable to explain the great discrepancy here 

 seen, as the new preparation both of the acid and the potash salt 

 had the same appearance as usual. Before proceeding to explain 

 how this discrepancy arose, I may state that the analysis just 

 given corresponds with the formula C^ H^^ 0^^, which requires 

 in 100 parts — 



Carbon 61*93 



Hydrogen 3*22 



Oxygen 34*85 



With the same specimen of potash salt as that employed for 

 the preparation of the acid, I made a quantity of silver salt by 

 dissolving the potash salt in water, and adding nitrate of silver. 

 A brilliant cinnabar-red precipitate fell, which was filtered, 

 washed and dried. It was not decomposed either by light or 

 by the heat of boiling water. 



0*5800 grm. of this salt, dried in the water-bath, gave 0*9800 

 carbonic acid and 0*1150 water. 



0*3310 grm., treated in a crucible with muriatic acid, and 

 heated until all the organic matter was destroyed, gave 0*1120 

 chloride of silver. 



These numbers lead to the following composition : — 



Eqs. Calculated. Found. 



Carbon ... 64 384 46*04 46*08 



Hydrogen . . 18 18 2*15 2*20 



Oxygen . . 25 200 24*00 24*37 



Oxide of silver 2 232 27*81 27*35 



834 10000 100*00 



2F2 



