//. EMOGLOBIN {REDUCED ILEMOGLOBIN). 231 
(</) Solution of sodium hydrosulphite (XallS* ).,).- — By the action of metallic 
zinc on a solution of sodium sulphate, in the absence of oxygen, a solution of 
intense reducing power is retained. Such a solution, which instantly decolor- 
ises indigo and litmus, reduces oxyhemoglobin. 1 
Methods of determining the percentage of haemoglobin have been based on 
this reaction,'- s though they have been abandoned as unreliable. 4 
(It) Solution ofhydrazin and it* salts. — It was pointed out byCurtius 5 that 
a solution of a salt of hydrazin reduces solutions of oxyhemoglobin with great 
rapidity ; and Hiifner 6 afterwards employed an aqueous solution of hydrazin 
hydrate to effect the reduction of concentrated solutions of oxyhemoglobin, 
the advantages of this reducing agent being that the only products of its 
decomposition are nitrogen and water, as shown in the following equation : — 
H 2 N— JS T H 2 .H 2 + 0. 2 = N 2 + 3H 2 0. 
(hydrazin hydrate) 
2. By taking advantage of the reducing action exerted by pro- 
ducts of putrefaction. — The solutions of oxyhemoglobin, or of diluted 
blood, is set aside in sealed tubes, when, especially at temperatures ap- 
proaching 40° C, reduction rapidly occurs. It is worthy of remark that, 
whilst oxyhemoglobin or its solutions very rapidly undergo change at 
temperatures above 0° C, such is not the case with reduced haemoglobin, 
which may be kept for many years in sealed tubes in the presence of 
putrefactive bacteria and the products of their activity. On opening the 
tubes and agitating with air, oxyhemoglobin is at once formed, and under 
favourable conditions may be crystallised. 
3. By taking advantage of the conditions which favour the 
"dissociation" of the compound of 2 with haemoglobin. — (a) By 
boiling in a "Toricellian" or barometric vacuum; (h) by subjecting 
diluted blood or a solution of oxyhemoglobin to the action of a 
long-continued stream of a neutral gas, such as hydrogen, nitrogen, or 
nitrous acid. 
4. By temporarily arresting the circulation through a suffi- 
ciently transparent part of the animal body. — It was first pointed 
out by Vierordt, 7 that the spectrum of oxyhemoglobin can be satisfac- 
torily demonstrated by bringing two fingers (preferably the fourth and 
fifth) close together and passing a beam of sunlight through the com- 
paratively thin layer of tissues at the boundaries of the adjacent fingers. 
He further pointed out that, on placing caoutchouc rings at the base of 
the first phalanges, after an interval varying between 40 and 300 
seconds (?), the tw T o bands of oxyhemoglobin became replaced by the 
single band indicative of reduced hemoglobin. 8 
1 Schiitzenberger and Risler, " Recherches sur le pouvoir oxydant du sang," Compt. rend. 
Acad. d. sc, Paris, 1873, tome Ixxvi. pp. 440-442, and pp. 1214-1216. 
2 Rollett, loc. cit. 
3 Ludwig and Schmidt, loc. cit. 
4 Quinquaud, "Sur uu precede de dosage de l'hemoglobine dans le sang," Compt. rend. 
Acad. d. sc, Paris, 1877, tome lxxvi. p. 1489. 
5 Journ. f. prakt. Chem., Leipzig, 1889, Bd. xxxix. S. 27. 
6 ; ' Bestimmung d. Sauerstoffscapacitat d. Blutfarbstoffs, " S. 156. 
7 "Das Hainoglobinspectrum am lebenden Menschen," Ztschr. f. Biol., Miinchen, 1876, 
Bd. xi. S. 188; and " Die Sauerstoffzehrung der lebenden Gewebe," ibid., 1878, Bd. xiv. 
S. 422. 
8 Refer to the following papers by A. Henoeque, " fitude spectroscopique du sang a la 
surface sous-unguc'ale du pouce," Compt. rend. Soc. de biol., Paris, Ser., 8, tome i. p. 671 ; 
and also "Notes complementaires," ibid., p. 700. According to this author, the average 
time of reduction, when the circulation through the thumb is arrested, varies between fifty- 
five and sixty-five seconds. 
