NIT
N I T
( 149 )
difference between tills and tbe pale nitric acidof the fame fpecific gravity. This was attemptedby heating the yellow acid, which, as alreadymentioned in this article, drives the fuperabun-dant nitrous gas out of the acid and leaves itpale and colourlefs. One hundred and fiftygrains of the yellow acid of 1.5. fp. gr. wereput in a fmall matrafs with a curved tube, andon the firft application of heat the colourchanged to a deep red. In a fhort time a redvapour appeared in the tube and was conveyedinto a noted weight of water by which it wasabforbed, giving the water a bright green co-lour. By continuing the heat the acid becamepale, and when cold was weighed and had loft15 grs. but its fpecific gravity was leffened to1.491 and 2| cubic inches of nitrous gas werecollected that had palled through the water un-abforbed. This experiment however was foundinconclufive, fince the nitrous gas expelled fromthe yellow acid in the procefs of its convevfionto the pale, had carried off with it in the formof nitrous vapour a portion of acid diflolved inthe gas. It was neceflary therefore to rcfort tothe fynthetical method, or that of impregnatinga given portion of the pale acid with nitrousgas. In a proper apparatus 90 grs. of the paleacid of 1.504 were introduced and nitrous gaswas thrown up, whereby the acid became warmand the colour changed firft to a pale ftraw,and as more of the gas was abforbed, to abright yellow. By tins 8 cubic inches of nitrousgas were abforbed, the acid gained 3 grs. inweight, and the fpecific gravity was diminifhedto 1.5. Thefe data were affumed as the meansof comparing the relative compofition of thepale and the yellow acid, both of 1.5 fp. gr.
The power of abforbing nitrous gas and thechange produced thereby on the acid was car-ried hill further, and the fame yellow acid of 1.5when returned into the apparatus became gra-dually, as the gas paffed into it, dark orange,light olive, dark olive, then of a muddy green,and laftly a blue green. This was the utmoftchange that the acid could affume, after whichthe nitrous acid appeared to pafs through theacid unaltered. The increafe of weight wasonly 1 grain and the fpecific gravity of the acidwas now only 1.474. On account however ofthe large quantity of nitrous gas which paffedthrough unabforbed, and the acid which wasvolatilized along with it, no accurate deduftionscould be drawn from the experiment, exceptthe great and fticcefiive changes of colour andthe great diminution of fpecific gravity. Aquantity cf this blue^ green acid faturated withnitrous gas was then put into a finall glafs ap-paratus and fiowly heated, when the nitrousgas was again given out with rapidity and theacid paffed back through the fucceflive coloursof green, olive, red, and orange, to a perfectlycolourlefs ftate, and when cold its fpecificgravity was then increafed from 1.47410 1.502.The quantity of blue green acid ufed was 04.25grs. and it had loft 31 grs. in paffmg to thecolourlefs ftate. The inferences from thefeand many other experiments (which from theircomplicated nature, and the numerous correc-tions required, on account of the folubility ofnitric acid in nitrous gas are only given as ap-proximations to the truth) and the relative pro-portion of ingredients in the different varietiesare given by Mr. Davy in the following tabularform..
100 parts
Sp. Gr.
Water.
Nitrous
Gas.
Pale nitric acid - - -
1.504
r 1
91-55
8-45
0.
Yellow nitrous - - -Bright yellow - - - -
1.502
i -5
<-w ]
0 i
90.588.9 +
8-3
8.1
12
2.9 6
Dark orange - - - -
1.480
p i
•l >
a 1
86.84
l - 6 .
5 - 5 6
Light olive' -----
1.479
86.
7-55
6.45
Dark olive - - - - -
1.478
S 1
85.4
7-5
7 -i
Bright green - - - -
1.476
!
84.8
7-44 .
7.76
Blue green -----
i -475
L J
84.6
7-4 •
8.
In a fecond table the refpeftive quantities ofoxygen and azot in different varieties of theacids are thus given, hut it muft be obfervedthat the oxygen fpecified is only that which be-
longs to the acid, and not to the water withwhich it is neceffariiy combined to give it aliquid form.