322 Mr. Knox’s experiments and observations 
the dry powders from the paper. It was suggested by Mr 
Wharmley, Chemical Assistant in the Laboratory of the 
Royal Society of Dublin. 
The alumina and iron thus collected, were boiled in caustic 
potash until a separation had taken place, the iron remaining 
as a powder at the bottom of the silver pan, and the alumina 
being held in solution by the alkali (d). 
The iron separated by the filter in the manner above men- 
tioned, was dried and weighed. It weighed 3,25 grains. It 
was then dissolved in muriatic acid, with which it effervesced, 
and therefore had been carbonated. A powder remained 
behind weighing 0,3 grain, which was silica. The iron was 
then precipitated by caustic potash, filtered, and again evapo- 
rated to dryness ; it weighed 3,4 grains, which gives of pro- 
toxide of iron 3,036 grains. 
The solution (c) evaporated to dryness and re-dissolved, 
left a residuum which weighed one grain, and which being 
insoluble in boiling sulphuric acid, and being perfectly white 
and gritty, I concluded to be silica. It was then precipitated • 
by carbonate of soda, filtered, washed and dried ; the pre- 
cipitate, which was carbonate of lime, weighed 2 grains. 
Now, 2 grains of carbonate of lime may be estimated at 1,12 
of lime. 
The alkaline solution (d) was precipitated while hot by 
muriate of ammonia, filtered, washed, and ignited in a pla- 
tina crucible ; it weighed 11,50 grains. 
Extraction of the alkali by acid. 
Nitric acid. 
100 grains of the pulverised stone were boiled with dilute 
