f 316 3 
by adding to it ad faturitatem a clear folution of 
an alcali, when the diflblved part will be precipi- 
tated, and fall to the bottom. For this purpofe 
the fal fod<e (Seft. xx.) may be very ufeful. 
SECT. LXL 
The acid of nitre will fulHce for making expe- 
riments upon {tones and earths *, but if the expe- 
riments are to be extended to the metals, the other 
two acids (Se6t. Ivii.) are alfo necelTary. As the 
acids are very corrolive, they mull not be kept in 
the ordinary Pocket-Laboratory, already deferibed, 
for fear of fpoiling the other apparatus, if the. 
{toppers ihould happen not to fit exa6tly to the 
necks 6i the bottles, and fome qf the ^cid ihould 
be fplit. 
SECT. LXIL 
I have a feparate box, v/hich is eight inches and 
three quarters long, four inches broad, and five 
inches high. In this box are three long and narrow 
bottles, containing the acids, placed upright at 
one end of it, two glafs matraifes laid horizontally 
in the upper part, and a little drawer underneath, 
made on purpofe to fill the empty room below the 
matrafies, and to give the box a regular form ; 
and as charcoal is not every where to be met with 
in travelling, I always have a piece in this drawer 
for the ufe of the Blow-pipe. 
SECT. LXIII. 
In order to keep the acids more clofe in the bot- 
tles, fince the glafs-flopper is not always fufficient, 
1 have a glafs-cover befides, made fo, as to ferew 
, round 
