34° Analyjis of water, and thereby a frefli portion of fixed air abforbed. When no more abforption and precipitation takes place, and all is cooled to the temperature of the atmofphere, then the lofs of the whole bulk of air in the receiver, will be obferved by the fcale on it, and the lofs indicates the quantity of fixed air which had lodged in that quantity of the fub ftance which had thus been examined. One cubic inch is very near equal to one grain of common medicinal weight, this way may be fufficient to afcertain the quantity of fixed air; and if we proceed in the fame manner with different fubftances, the refults muft pro portionally correfpond; we may indeed cal culate the quantity of fixed air of a fubftance thus tried already, pretty nearly from the quantity of gas which is firft collefted in the receiver, provided we are convinced that the earthy body thus treated, contains no other fubftance; as for inftance, metallic parts, vegetable or bituminous matter, which might thus by means of the acid, yield alfo a different gas, and which would confequently make the calculation erroneous or inaccurate; we may exp eft metallic matter, if the fubftance is co loured, vegetable matter when it deflagrates with nitre in the way before mentioned, - - and