f “72 ] 
in-any way. To the extremity of 
fuch a tube I adapt a hollow elafs 
ftopper of a conical form, fo ‘as to 
fit almoft all bottles. A brafs ring 
forced over the neck of the gum 
bottle preffes its fubftance againtt 
the glafs ftopper, and prevents the 
nitrous air rufhing out. 
It is to be obferved, that nitrous 
| aid will at laft deftroy the elaftic 
gum bottles by making its infide 
brittle, efpecially if the acid is very 
concentrated. 
Though good nitrous air may 
be obtained by many ways, yet-this 
| air lofes gradually its ftrength, and 
in a few days, if in contact with 
water, becomes very much weak- 
ened ; fo that it mutt be either made 
new almoft every day, or we cannot — 
be fure of the refult of the a 
_ iment. 
Be The 
