HIT 
of its atom is 5 , hydrogen being t. See Chemistry, 
vol. iv. p. 176. 
NITROS'ITY, f. Quality of nitre. Not in vfe. 
NI'TROUS, adj. Impregnated with nitre; confiding of 
nitre.—The northern air, being more fully charged with 
thofe particles fuppofed nitrous, which are the aliment of 
fire, is fitted to maintain the vital heat in that activity 
which is fufficient to move fuch an unwieldly bulk with 
due celerity. Ray. —Earth and water, mingled by the 
heat of the fun, gather nitrous fatnefs more than either 
of them have feverally. Bacon. 
He, to quench his drought fo much inclin’d, 
May fnowy fields and nitrous paftures find. 
Meet (lores of cold fo greedily purfu’d, 
And be ref re fil’d with never-wafting food. BTachmore. 
NI'TROUS A'CID. See Chemistry, vol. iv. p. 21 6. 
NI'TRUM, f. Nitre ; in mineralogy, a genus of falts. 
Generic characters—Of a fliarp, bitterifti, cooling, tafte; 
eafily foluble in water, and the l’olution not made turbid 
by a mixture of foda ; not eftervefcing with diluted acids, 
but, when faturated with concentrated fulphuric acid, 
emitting fharp fuffocating red vapours; detonates vio¬ 
lently when made red hot, and charcoal is thrown upon 
it. There are four fpecies. 
1. Nitrum nativum, nitre, faltpetre, or nitrat of potafti; 
fixed, pure, not deliquefcing in the air; when difloived 
and (lowly evaporated, cryftallizing into fix-fided prifms, 
terminated at each end by an unequal fix-fided pyramid. 
Found in Virginia, Spain, Sicily, India, Perlia, and China ; 
white, of a cooling tafte and refilling putrefaction : is very 
brittle, and foluble in feven times its weight of water ; 
when expofed to a ftrong heat it melts, and congeals by 
cooling into an opake mafs ; detonates very violently with 
combuftible bodies, particularly with phofphorus. Its 
principal ufe is in the compofition of gun-powder, which 
is made by mixing together feventy-fix parts of nitre, 
fifteen of charcoal, and nine of fulphur. It is called jal 
petra, or faltpetre, from its being often found attached to 
the ftone walls of buildings. 
In the Phil. Tranf. for 1814, Part II. there is a paper 
by Dr, Kidd, profefior of chemiltry at Oxford, entitled 
“ Obfervations refpeCting the natural Production of Salt¬ 
petre on the Walls of fubterraneous and otherBuildings.” 
The circumftance which occafioned Dr. Kidd’s obferva¬ 
tions was the appearance of an efflorefcence of nitre, on 
fome part of the walls of the laboratory of the Afhinolean 
Mufeum in Oxford. He gives a minute account of the 
conftruCtion of the building, its fituation, its materials, 
which are calcareous freellone, the parts on which the 
efflorefcence ufually appears, and other faCts connected 
with it which might feern to lead to a knowledge of the 
caufe. Of thefe the mod important is the ftate of the at- 
mofphere ; and the chief objeCt of this paper is to point 
out the connection between thefe circumltances. It is 
ftated that this formation of nitre never occurs except 
where lime is prelent, chiefly on buildings conftruCted of 
limeflone, but occafionally on bricks that are formed of 
a calcareous clay. From obfervations made on the fame 
part of the wall, and continued regularly for feveral 
months, Dr. Kidd found that a clear, frofty, and dry, 
(late of the atmofphere tended principally to the forma¬ 
tion of the fait; but that, in the molt favourable circum¬ 
ltances, it can never increafe beyond a certain limit. In 
a moift atmofphere, the formation is very flow, or is en¬ 
tirely fufpended ; and even the fait which had been formed 
gradually difappears. This difappearance has even taken 
place during frolt; and it does not feem to be owing to 
the fait being abforbed into the ftone. The nitre ob¬ 
tained from the walls in queftion was found, on exami¬ 
nation, to be nearly pure nitrat of potafii. In confider- 
ing the theory of this procefs, the author obferves that 
the only fublcances which appear to be efientially neceffary 
are atmofpherical air and limeflone. “ The component 
parts of nitrat of potafti, of which the faltpetre under 
HIT 107 
confideration almoft entirely confifts, are nitric acid, water, 
and potafii; which may be refolved into the following 
elements; oxygen, nitrogen, hydrogen, and potaflium; 
and all thefe elements are experimentally known to be 
prefent in the fituations where faltpetre is formed, with 
the exception of potaflium. In the fuppofition then that 
the faltpetre is a produCt and not an eduCt of the above 
procefs, fince no potafii can be detected either in the air 
or limeflone, the potaflium muft either be contained in a 
free ftate in the atmofphere or in tjhe limeflone, which from 
its remarkable attraction for oxygen is inadmiflible; or it 
muft be a component principle of fome one of the elements 
prefent; or laftly, it muft be itfelf a compound of two or 
more of the principles of thofe elements, or of two or more 
of the elements themfelves.” 
The calcareous caverns which abound in the ftate of 
Kentucky, furnilh large quantities of nitre. The earths 
which exilt in thefe caverns, and which contain both the 
nitrat of potafti and the nitrat of lime, are lixiviated ; and 
the lixivium is then made to pafs through wood-afiies, by 
the alkali of which the nitrat of lime is decompofed.' 
After due evaporation, the nitre is permitted to cryftallize. 
One of the molt remarkable of thefe caverns is in Madifon^ 
county, on Crooked Creek, about fixty miles fouth-eaft 
from Lexington. This cavern extends entirely through 
a hill, and affords a convenient paffage for horfes and 
waggons. Its length is 646 yards, its breadth is gene¬ 
rally about 40 feet, and its average height about 10 feet. 
One bufhel of the earth in this cavern commonly yields 
from one to two pounds of nitre; and the fame fait has 
been found to exift at the depth of fifteen feet; even the 
clay is impregnated with nitrat of lime. Kentucky alfo 
furnifiies nitre under a very different form, and confti- 
tuting what is there called the rock-ore, which is in faCt 
a fand-ftone richly impregnated with nitrat of potafii. 
Thefe fand-ftones are generally fituated at the head of 
narrow valleys which traverfe the fides of deep hills. 
They reft on calcareous flrata, and fometimes prefent a 
front from fixty to one hundred feet high. When broken 
into fmall fragments, and thrown into boiling water, the 
ftone foon falls into fand, one bufliel of which, by lixi- 
viation and cryftallization, frequently yields iolbs. and 
fometimes more than 2olbs. of nitrat of potafii. The 
nitre obtained from thefe rocks contains little or no nitrat 
of lime, and is faid to be fuperior for the manufacture of gun¬ 
powder to that extracted from the afore-mentioned earths. 
Mafles of native nitre, nearly.pure, and weighing feveral 
pounds, are fometimes found in the fiffures of thefe fand- 
ftones, or among detached fragments. Indeed, it is faid 
that thefe mafles of native nitre fometimes weigh feveral 
hundred pounds. Similar caverns occur in Tenneffee, and 
in fome parts of Virginia and Maryland. Cleaveland's 
Elementary Treatife on Geology ; Bolton, N. A. 1816. 
2. Nitrum humofum : fixed, not deliquefcing in the 
air, when difloived and (lowly evaporated cryftallizing into 
fix-fided prifms terminating at each end in a fix-fided un¬ 
equal pyramid, efflorefcing, mixed with mould or chalk. 
Found, generally in a ftate of white efflorefcence, on 
moift old walls which are but little expofed to the aCtion 
of the fur. and winds, as in wells, grottos, &c. efpecialiy 
thofe which face towards the fea. 
3. Nitrum cubicum : fixed, when difloived and eva¬ 
porated concreting into rhombic cryftals. Found, though 
rarely, in caves with the laft, efflorefcing from the moift 
fides of walls. 
4. Nitrum flammans : evaporating in fmoke when 
thrown on red-hot coals ; emitting an alkaline odour 
when rubbed together with quicklime, deliquefcing in. 
the air. Found with the Nitrum humofum. 
NI'TRY, adj. Nitrous: 
Winter my theme confines; whofe nitry wind 
Shall cruft the flabby mire, and kennels bind. Gay. 
NIT'TA, a town of Japan, in the ifland of Niphon s 
fifty miles north-north-weft of Jeddo. 
NITTAN'Y. 
