[ 1*9 3 
XXIII. Experiments on the TranfmiJJton of the Vapour of Acids 
thi an hot earthen Tube, and further Obfervations relating 
to Phlogijlon. By the Rev. Jofeph Prieftley, LL.D. F . R . S. 
Read July 2, 1789, , 
I N my late experiments on the phlogijlication of fpirit of nitre 
by heat it appeared, that when pure air was expelled from 
what is called dephlogifticated fpirit of nitre, the remainder 
was left phlogiflicated. This I find abundantly confirmed by 
repeating the experiments in a different manner, and on a 
larger fcale ; and I have applied the fame procefs to other acids 
and liquors of a different kind. From thefe it will appear, that 
oil of vitriol and fpirit of nitre, in their moft dephlogifticated 
Rate, confift of a proper faturation of the acids with phlo- 
gifton, fo that what we have called the phlogiftication of them, 
ought rather to have been called their juper-phlogiftication. 
I began with treating a quantity of oil of vitriol as I had 
done the fpirit of nitre, viz * expofing it to heat in a glafs tube, 
hermetically fealed and nearly exhaufted ; and the refult was 
fimilar to that of the experiment with the nitrous acid, with 
refpedl: to theexoullion of air from it, though the phlogifrica- 
tion not appearing by any change of colour , I did not in this 
method afcertain that circumftance, The particulars were as 
follows. 
i\fter the acid had been made to boil fome time, a denfe 
white vapour appeared in quick motion at a diflance above the 
acid, 
