and the feeming Convcrfon of Water Into Air. 4 1 3 
iron, which could only give inflammable air. I would obferve* 
that the melted iron formed itfelf into large balls, which ap- 
peared to be a mere fag or glafs, and was no longer iron. 
Afterwards, to put this hypothelis concerning the confli- 
ct uent^ principles of fixed air to a more diredl proof, I mixed 
iron which gave only inflammable air, with ’red preci- 
pitate, which I found to give nothing but the pureft dephlo- 
gifticated ; and when I heated them in a coated glafs retort, 
they gave a great quantity of fixed air, in fome portions of 
winch nineteen- twentieths were abforbed by lime-water ; but 
the refiduum was inflammable. However, when 1 mixed with 
iron tilings a quantity of powdered charcoal, which 1 had 
found to give only inflammable air, the fixed air produced from 
it was to pure, that only one- fortieth part of it remained un- 
abforbed by water ; fo that this fixed air was as pure as that 
which is generally procured from chalk by oil of vitriol. 
It appeared, in fome of thefe experiments, that three ounce 
meafutes of dephlogiflicated air go into the compolition of two 
ounce meafures of fixed air. For one ounce of this red preci- 
pitate gave 60 ounce meafures of dephlogiffated air; and when 
mixed with two ounces of iron filings, it gave about 40 ounce 
meafures of fixed air that were actually abforbed by water, be- 
iides a refiduum that was inflammable. I had the fame pro- 
portion when I ufed half an ounce of each of the materials. 
But when I ufed one ounce of each, I got only 20 ounce mea- 
lures of fixed air, including the refiduum. At other times I 
had different proportions with different quantities of iron filings 
and charcoal. 
I cannot conclude thefe obfervations without taking notice, 
how very valuable an inftrument in philofophy is a good burn- 
ing lens. I his muff have been perceived in many of my 
former 
