C 94 - ] 
^ The water remaining after diftillation, and from 
which the earth was feparated, was evaporated, firffc 
in a fiiver pan, and afterwards in a glafs cup, till it was 
reduced to about three ounces. Not the leaft earth 
was precipitated during the evaporation, till it was 
reduced to a fmall quantity ; there then fell 39 grains, 
which were entirely felenite: fo that all the unneu- 
tralized earth in the water was feparated during the 
diftillation. The liquor thus evaporated was of a 
reddifh colour, like an infufion of foot. 
Many waters contain a good deal of neutral fait 
compofed ot the nitrous acid united to a calcareous 
earth ; the molt convenient way of afcertaining the 
quantity of which, is to drop a folution of fixed alcali 
into the evaporated water, till all the earth is preci- 
pitated 5 whereby this fait is changed into true nitre, 
and is capable of being cryftallized. For this 
reafon, fome fixed alcali was dropt into the eva- 
porated water till it made no farther precipitation. 
The earth precipitated thereby weighed thirty-fix 
grains, and was entirely magnefia. The liquor 
was then farther evaporated, but no nitre could be 
made to fhoot : being then evaporated to drynefs, 
it weighed 256 grains. It gave not the lead figns of 
containing any nitrous fait, either by putting fome of 
it upon lighted charcoal, or by making a match with 
a folution of it, but appeared to be a mixture of fea 
fait and vitriolated tartar, or fome other fait compofed 
of the vitriolic acid. As I have heard of no other 
London water, that has been examined with this 
view, but what has been found to contain a confidcr- 
able proportion of nitrous fait, it feems very remark- 
able that this fhould be intirely deflitutc of it. I now 
proceed 
