297 



duction of a substitutive product which does not crystallize, and can- 

 not be obtained pure. Its analysis gave as the mean of four closely 

 concordant experiments — 



Mean. Calculation. 



Carbon, . 69-112 Gol? C^^ 132^ 



Hydrogen, . 5-550 526 H^^ 10 



Oxygi 



en. 



25-333 25-27 O, 48 



100-000 100-00 



corresponding with the formula C,_^ Hj,, Og ; but the impossibility 

 of forming compounds renders it impossible to ascertain whether this 

 correctly represents its constitution. 



2. When the colouring matter is boiled with alcohol the pheno- 

 mena are materially difierent ; for the filtered solution deposits, on 

 cooling, a pale flocky amorphous substance, which is obtained pure 

 by repeated crystallization. It is insoluble in water, readily soluble 

 in hot, sparingly in cold alcohol, and scarcely at all in ether. Its 

 analysis gave results which agree with the formula C^g JI^^ Og. 



3. The red alcoholic solution from which the flocky matter has 

 been separated leaves an evaporation or dark red amorphous resin, 

 meltiniT at 212^ It gives a red precipitate with acetate of lead, 

 but the compound could not be obtained of definite composition, and 

 it seems not improbable that the resin may be a mixture of several 

 different substances. The author found the proportion of oxide 

 of lead to vary between 18-67 and 34 per cent., according to the 

 conditions under which the precipitation was effected. The resin, 

 on analysis, gave results which agree pretty well with the formula 

 r Tf O which is in accordance with the lowest proportion of 

 oxide of lead obtained from its compound, but none ot the other re- 

 sults can be brought into relation with it. 



The colouring matter of the Rottlera belongs to the class of sub- 

 stantive dyes, and does not require the intervention of a mordant. 

 It gives a very fine flame colour on silk, but to calico, with or with- 

 out mordants, it gives only a pale fawn colour, entirely devoid of 

 beauty. The author considers it worth the attention of silk dyers 

 in this country. 



