422. Mr. War's Method of preparing a Tel Liguor, &c. 
or of the fixed or volatile alkali. But it 1s neceflary to. obfervé,,. 
that if the liquor has an. excefs | of alkali, it will foon lofe its 
colour, and become yellow, from’ which ‘late it cannot be 
reftored; therefore care thould be taken to bring i it very saat : 
to a blue, and_not to let it verge towards a green™. os ae 
3. By the fame procefs I have made a red infufion of bis, : 
which, on being neutralized, forms at prefent a very fenfible 
teft;. but how long it will preferve its properties I have, not 
yet determined. ‘Probably the coloured infufions of. other, 
flowers may be preferved in the fame manner, by the antifeptic; 
power of the vitriolic. acid, fo.as to lofe little of their original 
fenfibility. Paper, frefh {tained with thefe tefts in their neutral 
ftate, has fufficient fenfibility for many experiments; but the; 
alum/and glue which enter into the preparation of writing- 
paper feem in fome degree to fix the colour; and paper which 
is not fized becomes fomewhat tranfparent, when wetted, » 
which renders {mall changes of colour imperceptible; fo that 
where accuracy is required, the teft fhould. be ufed-in a liquid 
{tate +. 





* Since writing the above, I have found, that the infufions of red cabbages ’ 
and of various flowers in water acidulated by means of vitriolic acid, are apt to 
turn mouldy in the fummer feafon, and alfo that the moulding is prevented by the 
addition.of fpirits of wine. The quantity of fpirit which is neceffary for this 
purpofe I have not been able to afcertain; but 1 add it by little at a time, until 
‘the progrefs of the moulding is prevented. 
+ I have found, that the petals of the fearlet rofe, and hole of the pink- 
coleured lychnis, treatedin this manner, afford very {enfible tefts. . 
REA 
Ge 
