398 PROCEEDINGS OF SECTION B. 
influence the precipitation of another, under certain circumstances ; 
it struck the author there might be something present in the 
original mineral, precipitable by sulphuretted hydrogen from an 
acid solution, capable of carrying down large quantities of zinc 
sulphides. In order to settle this question, recourse had to be 
made to the balance, a weighed portion of the sulphide was 
converted into oxide by ignition in a porcelain crucible, in order 
to get the ratio between them. This method of procedure proved 
a failure; for, upon stronger ignition over a blast lamp, a brown 
sub-metallic film condensed on the cool part of the crucible cover, 
showing the sulphide to be impure. This sublimate proved upon 
examination, to be cadmium oxide; a second deposit was obtained 
in a similar manner on prolonged heating, and on testing found 
to be lead oxide.* 
When no further sublimation could be detected, a weighed 
quantity of the residual oxide was converted into sulphate by 
dissolving it in dilute sulphuric acid, afterwards removing the 
excess of acid by evaporation, finally heating to a temperature 
near redness, so as to render the salt anhydrous. The weight 
being taken after cooling, the ratio between the oxide and 
sulphate was found to correspond almost exactly with zine.t 
Experiments with the view to find out the exact conditions 
necessary for the precipitation of zine from acid solutions by 
hydrogen sulphide were made. The result of these proved, 
tirstly, that zinc is precipitated from solutions as long as the acid 
does not exceed one per cent; secondly, if the temperature of the 
solution be raised, the quantity of acid required to prevent 
precipitation is less. 
It would appear the conditions vary according to the ratio of 
zinc salt to the free acid in a given volume of solution, the 
duration of the experiment having also considerable influence. 
11.—ON THE COLOURING MATTER OF DROSERA 
WHITTAKERI. 
By E. H. Renniz, M.A., D.Sc., Professor of Chemistry in the 
University of Adelaide. 
THE species of Drosera above named is found growing plentifully 
in the hills in the neighbourhood of Adelaide. The bulb, which 
is found attached to each plant at a depth of from three to four 
inches, contains colouring matter which can be extracted by 
boiling alcohol. On evaporating off the spirit a residue remains, 
* These facts are mentioned here as they may be found useful in the detection of traces 
of cadmium and lead. 
+ Examined spectroscopically, it contained nothing but zinc, except traces of cadmium 
and lead. 
