NITRIC OXIDE HAEMOGLOBIN. 24I 
converted into a black shining mass, which when spread in thin layers 
over porcelain appears of a greenish-brown colour } 
4 Aqueous neutral solutions of pure CO-ha?moglobin when heated 
to boiling point furnish a bright red precipitate, confposed , f ,, ■ 
albuminous substances and CO-ha3mochromogen (Hoppe-Sevler) 
, ' K Solu tionsoi carbonic oxide haemoglobin, treated with NO in the 
absence oi oxygen, are at one,- decomposed, and liberate CO (HiirnS) 
Nitric Oxide Hemoglobin (XO-H,emoglobin). 
Mode of preparation.— So great is the affinity of nitric oxide for oxygen 
that, when lt comes in contact with it, deep red fumes of nitrogen peroxide NO 
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indicated in the following equation occurs : 
3X0, + H 2 = 2HX( ), + NX). 
But as all free acids decompose the colouring matter of the blood before 
causing nitric oxide to act upon blood certain precautions must be tak • 
for even if atmospheric oxygen be eliminated and nitric oxide caused to act 
upon oxyhemoglobin, nitrous oxide would he formed at the expense of the 
oxygen of that body; and next, by the action of water, nitr^add which 
would immediately decompose the hemoglobin. ' 
Two methods of proceeding are open to us— (a) To add to the solution of 
oxyhemoglobin which is to he subjected to the action of nitric ox defficln 
alkali to neutralise the nitric acid which will be formed. Siicl t a solution 
must be placed in a flask, permitting of the whole of the air above the ol ton 
being driven out and replaced by a neutral gas, before allowing access to Z 
nitric oxide. After the latter has exerted its action, care mus % taken a, 
trac^f E%J?^* ^ " ^ * *° - * -ovTall 
(6) The solution of oxyhemoglobin is subjected to the long-continued 
action o carbonic oxide, so as to form CO-hemoglobin and to expel all race* 
ot dissolved oxygen. Otherwise, the process is constructed is described 
TX$etZ*0 V :r S8 T W bG CGrtainIy Pr6ferred ' if * -rTdesS to 
ei}. stance the A U-compound. 
Physical and chemical characters.— Blood saturated with nitric oxide 
possesses almost as florid a colour as CO-blood, though Hermann says 
that it does not present the slight bluish shade of the fatter. ftSiflK 
exln-tit r Sln n ,S0lUt r S ° f Np-^^globin, or diluted NO-blood 
exhibit a visible spectrum m which, as I have convinced myself the 
bands occupy precisely the position of the two oxyhemoglobin ban Is 
In the photographic spectrum, however, the band in the extreme Set 
exhibits absolute coincidence with that of CO-hamioglobin 
NO-ha3moglobin can be crystallised, and, as Hermann showed the 
crystals are identical with those of oxyhemoglobin and CO-haamoglobin 
Alleged (but Problematical) Compounds of Hemoglobin 
with Gases. 
Wn 1 " ^^ h7 f r0 °y ani0 a cid.-The most discrepant statements have 
been made in reference to the very simple question- whether h y drocyanic 
siTectn mf T" Tl t^X bl °° d ?"* ** Ch ™ Ct ™ ° f **£$££ 
spectrum. In spite of these, it may be definitely stated that, at ordinary 
temperatures, and when acting for moderate periods, hydrocyanic acid leads 
VOL. I. 1 6 
