ns F U M I G 
pounds; wlietlier they are always accompanied by carbo¬ 
nic acid gas ; and, lafily, whether the vegetable acids are 
capable of affeiting decompofition. Such are the points 
which this author undertakes to difciifs, and to deter¬ 
mine by chemical experiment. 
With this view, fotne pieces of raw beef were inclofed 
under a large glafs bell filled with atmofpheric air, and 
inverted over water, and left to putrefy in this ftate. 
When the putrefaclion was complete, the air contained 
in the glafs was expofed to different trials ; and the fol¬ 
lowing is the refult in general terms. When the air was 
vvaflied with lime-water, a copious precipitation took 
place, marking the prefence of carbonic acid gas. The 
air preferved, neverth.elefs, its putrid fmell. Another 
portion of the putrid air was agitated with a folution of 
nitrate of ftlver, which became infiantly blackened, and 
a brownifh pellicle formed on the furface, part of which 
funk to.the bottom of the vefTel. Nearly the fame phe¬ 
nomena took place with the nitrates of mercury and cop¬ 
per, and with the acetite of lead. 
The putrid gas being introduced into a bottle with a-fo- 
lution of fulphtir of lime, the latter foon grew turbid, 
and carbonate of lime was depofited, but without any ap¬ 
pearance of a black or brown precipitate, or the difen- 
gagement ^f ammoniac. Nor did Hips of paper, tindlur- 
ed with different vegetable colours, or with nitrate of 
copper, undergo any change on expofure to putrid gas, 
’which indicated in any degree the prefence of ammoniac, 
or otlier alkali in a free ftate. When, however, quick¬ 
lime was added to the water which had been in contadT; 
with the putrid gas, and which had abforbed fufficient 
of this to give it an offenfive odour, a vapour was difen- 
gaged from the water which fenfibly evinced the prefence 
of ammoniac. 
When the air was agitated with a folution of fnlphate 
of zinc, there was no trace of tire white precipitate which 
fulphurated Itydrogen, and the hydro-fulplnires, occuflon 
in that liquor: nor was the putrid odour diminifhed in 
any remarkable degree. The oxyds which are known to 
adl moft powerfully on the hydro-fulphures, fuch as the 
oxyd of zinc, fhe Islack oxyd of manganefe, and the 
brown oxyd of lead, all reduced to fine powder, and 
nightly moiftened with diftilled water, were fluit up in 
contadt with the putrid gas : but, after twenty-four hours 
of expofure in this way, no change in the colour of ihofe 
oxyds was perceptible, no trace of tive difengagement of 
ammoniac, nor any phenomenon indicating the prelence 
of fulpluir. The fetid odour merely appeared to be fome- 
what diminiftied in the veflel containing the oxyd of nian- 
ganeie, and the water acquired the property of precipi¬ 
tating, of a dirty grey colour, the folutions of nitrate of 
meicury and of the acetite of lead. 
In the putrid air was next burnt a confiderable quanti¬ 
ty of g,um benzoin; but the effedl: was merely to cover, 
in fome degree, its offenfive odour, without at all deftroy- 
ing it. The effedl was the fame when the air was agitated 
with fpirituotts folutions of different aromatic gums and 
balfams. When the thieves’ vinegar was employed in 
the fame way, the putrid odour was modified merely, 
but not deftroyed. The pyro-ligneous acid feemed to 
have rather moreeffeft, as, after two hours, a flight de¬ 
gree only of offenfive fmell was perceivable, combined 
with the empyreumatic odour of the acid. When gun¬ 
powder was repeatedly exploded in the gas, the offenfive 
odour difjppeared; but it feemed rather to he owing to 
the difperfion of the gas than to its corredtion. The 
gafes produced, indeed, during the explofion of gunpow. 
der, being merely carbonic acid and azo-tic gas, with a 
very confiderable proportion of fulphiireous gas, could 
not be expected to act chemically on the ptitrid vapour. 
Good vinegar caufed the putrid odour to difappear;'asdid 
the vapour of diftilled vinegar. Wlien the acetic acid, 
or radical vinegar, was fubftituted for the two former, 
theefi’eti was much more ftriking, the fetid odour difap- 
A T I O N. 
pearing inftantly, without the agreeable pungency of the- 
acid being fenfibly diminifhed. 
The mineral acids were next examined, as to tlieir 
power of deftroying the contamination of putrid air. The 
vapour of fulphiireousacid, and the fame in a ftate of gas, 
let loofe during the combiiftion of fiilphur, were very 
effeftiial for the purpofe. The fulphuric acid, both con¬ 
centrated and diluted with-three times its bulk of water, 
completely deftroyed the putrid fmell when agitated with 
the air. When the nitric acid vapour was employed, in 
the manner recommended by Dr. Smyth, no traces of 
putridity remained, nor did the air occafion any alteration 
of colour in ihe folutions of acetite of lead or of nitrate cf 
mercury. 
Whatever care was taken in the execution of the laft 
experiment, the author always obferved fome flight tra. 
ces of red vapours of nitrotis gas during the procefs : he 
proceeded, therefore, to afeertain, by direfl experiment, 
whether the opinion-of Mr. Keir was well founded, that 
oxygen gas is given out during the procefs, and thus the 
air meliorated by it. Probability, certainly, was againfl 
fuch a fuppofition ; for it would be furprifing, if a diftiU 
lation, the eflential and rigorous condition of which is, 
that not a particle of acid is decompofed, fliould furnifti a 
fenfible quantity of oxygen. But the author ftill lefsex- 
pefted to find, that, in oppofition to Mr. Keir’s affertion, 
inftead of being melioraited by the procefs, tlie air was 
rendered worfe by many degrees than before. This, how¬ 
ever, was the faiT. 
The powerful aiSlion of the muriatic acid gas has been 
already mentioned. On repeating the experiments of 
Mr. Cruickfliank with the oxygenated muriatic acid gas, 
the author’s refiilts fully confirmed thofe of that gentle¬ 
man. The advantages of this procefs, efpecially when 
fimplified in the way here advifed, are clearly demon- 
ftrated. Into a bottle, whofe capacity was three centili¬ 
tres (about ^oz.) were put four grammes (about of 
black oxyd of manganel^e, grofsly powdered ; the bottle 
then filled about two-thirds full with the nitro-muriatic 
acid (aqua regia). In a few minutes, on being agitated, 
the oxygenated muriatic acid gas was difengaged with 
fuch intenfity, that vegetable colours prefented to the 
mouth of the bottle were foon radically deftroyed. The 
facility, and particularly the promptitude, with which, 
without the aid of a diftilling apparatus, this powerful re¬ 
agent is thus obtained, induced the author to give it the 
name of extemporaneous oxy-muriatic acid-, and he after¬ 
wards difeovered another property of this preparation, 
which may render it ftill more generally iifeful. It is 
well known how difficult it is, even in the clofeft veflels, 
to preferve unchanged the oxygenated muriatic acid, as 
procured by the common procelfes. A bottle prepared 
in the manner here indicated, after being laid afide and 
forgotten for eight years, was found to have retained its 
priftine pungency. 
Havingithus examined the power of the various fub- 
ftances employed for the deftrudtion of contagion, the 
author gives a general view of the conclufions deducible 
from his experiments’with refpedl to the comparative ef¬ 
ficacy of the different means ; and points out the beft me¬ 
thod of employing thofe which are moft deferving of con¬ 
fidence. Water, cold or warm, employed in waftiing, 
may carry away infedfious matter, but without decom. 
pofing it: and it has been found that lye itfelf has not al¬ 
ways deftroyed the contagion imTinen; but that this has 
afterwards communicated the infedlion, in the cafe of 
plague. Lime is only really iif^fut for decompofing ani¬ 
mal matters before putrefadiion begins, or for the abforp- 
tion of carbonic acid; for putrid air is not fweetened by 
parting through lime water. Refinous fubftances, even 
thofe Vvhich give out a volatile acid on diftillation, merely 
difguife tlie putrid miafmata, without at all deftroying 
them, or changing their infedtious nature. Fire occafions 
currents of air, which may carry off and difperfe putrid 
vapoursg 
