Massey on Saltpetre. 133 



have its origin in putrid substances ; but to this there are 

 likewise many objections. In the first place, the recent juices 

 of vegetables and animals, some few of the former excepted, 

 if we are not mistaken, contain no kind of acid whatever, 

 and in a putrid state everybody knows they are of a 

 volatile alkaline nature, which being the most powerful 

 objection, we shall here principally endeavour to remove, 

 and upon the whole shall undertake to show that there is 

 an original acid in all vegetables and animals, which being 

 rendered volatile by putrefaction, assumes the specific cha- 

 racter of the nitrous. And that, since this acid constantly 

 arises in vapour from putrid substances, hence it is that 

 the rubbish of old houses, and of old clay walls, become 

 impregnated with it, as well as those earths that lie in 

 conjunction with thern. 



' That the recent juices of vegetables and animals are 

 in general perfectly neutral, we shall readily admit ; but 

 from hence we think it does not follow that they contain 

 neither an acid nor alkali, as is commonly concluded ; on 

 the contrary, we apprehend a more just inference is that, 

 being mixed, they must necessarily contain both. It is 

 certain that if we throw a calcareous earth or fixed salt into 

 any of these juices, the earth or salt will be neutralised by 

 it ; which we take to be a proof that it contains an acid, 

 which quits the weaker to join with the stronger alkali, 

 according to the law of affinities. 



'And the case will be the same, if these juices are 

 putrefied. If we throw a fixed salt into any putrid liquor 

 it will be neutralised by it, and now, if we dip a piece of 

 soft paper into this mixture and dry it, it will burn like a 

 match, in the same manner as if dipped into a weak solu- 

 tion of saltpetre ; which shows, that it not only contains 



