272 Mr. Keir’s Experiments and Observations on 
nitrous gas were expelled, and the (elution then acquired a 
bl ue colour. 
25. In the fame apparatus and manner, 100 grain-meafures 
of the impregnated oil of vitriol were applied to tin, which 
was thereby diminifhed in weight 16 grains, while the liquor 
acquired a violet colour, became turbid by the fufpenfion of 
the calx of tin, and a quantity of nitrous gas was thrown into 
the inverted receiver equal to 4100 grain-meafures, without 
application of heat, and another quantity equal to 4900 grain- 
meafures, after the retort was put into the water-bath. 
26. Mercury added to the impregnated oil of vitriol formed 
a thick white turbid liquor, which was rendered clear by addi- 
tion of unimpregnated oil of vitriol. In a little time this 
mixture continuing to a£t on the remaining mercury acquired a 
purple colour. The mercury adted upon funk to the bottom of 
the glafs in the form of a white powder, and the purple liquor, 
when mixed with a folution of common fait in water, gave no 
appearance of its containing any mercury in a diffolved ftate. 
27. The nitrous gas with which the oil of vitriol is impreg- 
nated (hews no difpofition to quit the acid by expofure to air; 
but, on adding water to the impregnated acid, the gas is ex- 
pelled fuddehly with great effervefcence, and with red fumes, 
in confequence of its mixture with the atmofpherical air. 
Upon adding 240 grains of water to 60 grain-meafures of 
impregnated oil of vitriol, 2300 grains of nitrous gas were 
thrown into the receiver ; but as the adtion of the two liquors 
is inftantaneous, the quantity of gas expelled from the retort 
before its neck could be immerfed in water, and placed under 
the receiver, muft have been confiderable. The whole of the 
gas, however, was not extricated by means of the water, for 
the 
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