314 - Chemistry. 
magnesia when introduced before the condensed ignited gas, en 
tered into rapid fusion, and formed a beautiful black bead. 
1 am, sir, your obedient humble servant, 
Douglas, Is!e of Man, Sept. 17, 1817, J. Muar: 
The following errata appear in my late paper: Pagel 45, line 8, 
read “ while” fustead of until, Page 144, read ** of ihe corrosive 
salt.” Page 146, read Mr. Porrett j Pes J.M. 
PROCESS FOR PREPARING ACETATE OF POTASH :—COLOURING 
MATTER OF DRAGONS BLOOD EXTRACTED BY QUICKLIME. 
To Mr. Tilloch. 
Srr,—I beg leave to offer to the consideration of your che- 
mical readers a more convenient process for preparing acetate 
of potassa than that which is at present followed, in the way 
now practised; viz. that of saturating subcarbonate of potassa 
with distilled vinegar. It almost invariably happens that the so- 
lution is of a brown colour, probably arising in part from the pre- 
sence of some extractive matter, and partly from the partial com- 
bustion of the acid during the ebullition. In order to remove this 
impurity the solution is evaporated to dryness, and the residaum 
is melted by a gentle heat and left to crystallize. If the solution 
of the acetate be made in the way which I shall proceed to di- 
rect, it is colourless, and cousequently does not require the eya- 
poration to dryness ‘and subsequent fusion. 
Let 120 parts of subcarbonate of potassa and 300 parts of 
superacetate of lead be separately dissolved in as little water as 
possible; the solutions are to be mixed together, the carbonate 
of lead will be precipitated, and the acetate of potassa will re- 
main in solution, which may be evaporated until it becomes 
somewhat thick, and then set aside to crystallize. 
Iam unacquainted with the quantity of acetate yielded by the 
above proportions ; as while the solution was evaporating, an 
accident happened to my apparatus. 
I obtained from the 300 grains of superacetate only 160 grains 
of carbonate of lead; from which circumstance I ani induced to 
question the accuracy of Thenard’s statement of the proportions 
of the component parts of the former salt; viz. oxide of lead 58; 
acetic acid 26; water 16: for, supposing his account to be 
correct, I did not obtain the full proportion of oxide, without 
reckoning the carbonic acid; the whole of which, as no efferves- 
cence occurred on mixing the solutions, must have entered into 
combination. I am, sir, yours respectfully, 
July 27, 1817. LITHOPHILUS. 
P.S. [have recently found that the colouring matter of the 
resin vulgarly denominated dragons blood, may be extracted by 
quicklime, almost if not quite as well as by caustic alkali, 
