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



After making the due corrections for the ash in the way just 

 described, these numbers correspond in 100 parts to — 



I. II. III. IV. 



Carbon . . . 5666 5681 56*06 5646 

 Hydrogen . . 6-13 550 5*54 5-45 



Oxygen . . . 3721 37*69 38*40 3809 



leading to the formula C^' H^* 0*^ as the following calculation 

 shows : — 



Eqg. Calculated. 



Carbon ... 56 336 56*75 



Hydrogen . . 32 32 5*40 



Oxygen ... 28 224 37*85 



592 100*00 



The lead compound was prepared by dissolving the substance 

 in a small quantity of water, adding an alcoholic solution of 

 acetate of lead, separating the red precipitate which was formed, 

 by filtration, adding a little ammonia to the filtered liquid, 

 taking care to leave an excess of rubidehydran in solution, fil- 

 tering the precipitate and washing it with alcohol. 



0*5705 grm. of this precipitate, dried in the water-bath, gave 

 0*6110 carbonic acid and 0*1465 water. 



0*3180 grm., treated with sulphuric acid and heated, left 

 0*2200 grm. residue, which on being treated with hot water, 

 yielded to the latter 0*0140 grm. sulphate of magnesia, leaving 

 0*2060 sulphate of lead. 



These numbers lead to the following composition : — 



1150*5 100*00 

 The deficiency in the oxide of lead in this analysis arose 

 without doubt from the oxide being in part replaced by mag- 

 nesia. 



It appears therefore that rubidehydran diff'ers from rubian 

 merely by containing the elements of two equivalents of water 

 less, and the origin of the different products of decomposition 

 to which it gives rise may therefore be explained in the same 

 manner as in the case of rubian. 



Of its products of decomposition with acids 1 only obtained 

 alizarine in quantities and of the degree of purity requisite for 

 analysis. It had the usual composition of that substance, as the 

 following analysis will show : — 



