[ 3'3 ] 
XIX. Additional Experiments and Obfervations relating to the 
Principle of Acidity , the Decompofition of Water y and Phlo - 
glfton. By Jofeph Prieftley, LL.D . F. R *S. With Letters 
to him on the Subjedl, by Dr. Withering, and James Keir, 
Read May I, 1788. 
W HEN I wrote the Paper, which the Society has done 
me the honour to order to be printed in their Tran- 
fa&ions, I had found that the decompofition of dephlogifti- 
cated and inflammable air, by means of the ele&ric fpark, 
produced an acid liquor , which Dr. Withering found to be 
the nitrous ; though I fhould have obferved, that he exprefled 
fome doubt whether the liquor did not alio contain fome other 
acid befides the nitrous. 
I have lince that time been defirous to afcertain the quantity 
of acid producible from a given quantity of air ; and with this 
view I gave Mr. Keir as much of the liquor as I had coT 
Ie£ted from the decompofition of about five hundred ounce 
meafures of dephlogiflicated air, and the ufual proportion of 
inflammable air mixed with it. The liquor, he informed me, 
was 442 grains, of the fpecific gravity of 1022 (that of water 
being 1000) and that it contained as much acid as was equi- 
valent to I2.c;4 grains of concentrated acid of vitriol; which* 
(quantity of vitriolic acid is capable of fatu rating as much ve- 
getable fixed alkali as is contained in 22$ grains of dry nitre, 
5 
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