296 Mr. Walker’s Experiments on the 
natron is to be added to the diluted acid, the mixture well 
ffirred, and immediately afterward the powdered nitrated am- 
monia, again ftirring the mixture : to produce the greatefl 
effect, the falts fhould be procured as dry and tranfparent as 
poffible, and ufed freffily powdered. Thefe feem to be the 
heft proportions when the temperature .of the air and ingre- 
dients is +50° ; as the temperature at fetting out is higher or 
lower than this, the quantity of the diluted acid will evi- 
dently require to be proportionably diminiffied or increafed. 
This mixture is but little inferior to one made by diffolving 
fnow in nitrous acid, for it funk the thermometer from +32° 
to - 20 0 ; perhaps it may be poffible to reduce the falts to fo 
fine a powder as to make it equal. In this laff experiment the 
diluted acid was equal in quantity to the vitriolated natron, 
being four parts each, the nitrated ammonia three and a half 
as before. A powder compofed of muriated ammonia (crude fal 
ammoniac) five parts, nitrated kali (nitre) four parts, mixed, 
mav be fubftituted in the ftead of nitrated ammonia, with 
nearly equal effe<ff, and in the fame proportion. 
Cryftallized nitrated ammonia, reduced to very fine powder, 
funk the thermometer, during its folution in rain-water, forty- 
eight degrees, from + 56°, the temperature of the air and ma- 
terials, to +8° j and when evaporated gently to drynefs, and 
finely powdered, it funk the thermometer forty-nine degrees, 
to + 7 0 , the temperature of the air and materials being as be- 
fore at + 56° : therefore, in this fait (which produces, as ap- 
pears above, much greater cold during folution in water, than 
any other hitherto known) the water of cryffallization is not in 
the lead: conducive to that effedt . I expe&ed, that by diluting 
the ftrong nitrous acid to the proper ftrength with fnow, in- 
ftead of water, by which its teoaperature would be much 
reduced,., 
