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DR. A. GAMGEE ON THE ACTION OE NITRITES ON BLOOD. 
led to find that the optical properties of blood were considerably modified by the action 
of nitrites. I embodied the results of my first observations in a preliminary note which 
I read before the Royal Society of Edinburgh on the 4th of March, 1867 l . At that time 
I was acquainted with little more than the changes in the optical characters induced by 
nitrites. 
The nature of the changes and the influence which they exert upon the relation of 
the blood to gases are chiefly to be discussed in the present paper. 
I. On the Changes in the Colour of the Blood induced by Nitrites. 
When defib rinated and well-arterialized blood is mixed with a solution of nitrite of 
potassium or nitrite of sodium, its colour becomes almost immediately altered ; from its 
beautiful florid-red it changes to a more or less chocolate-brown colour. The rapidity 
with which this change takes place appears to vary considerably in the case of different 
samples of blood. Just as great differences are found to exist in the relative rate with 
which the colour of blood (and its spectrum) is affected by standard solutions of alkalies 
and acids, so considerable variations occur in the rapidity of the action of nitrites. In 
the course of this investigation the nitrites whose action on blood has been chiefly 
examined have been those of potassium, sodium, silver, and amyl. The alkaline nitrites 
were always prepared by decomposing repeatedly crystallized nitrite of silver by means 
of an exactly equivalent quantity of the alkaline chloride. The nitrite of amyl was pre- 
pared by the action of nitrous acid upon repeatedly fractionated amylic alcohol. The 
product was also repeatedly fractionated, and only those portions which boiled between 
95° and 100° C. collected as pure. 
The differences in the rapidity with which nitrites and other active substances act 
upon blood, probably depend much upon physical conditions affecting the blood-cor- 
puscles. The freshly-drawn blood of the Dog is almost instantaneously affected in 
colour when mixed with solutions of nitrites, whereas in the case of the blood of the 
Ox and Sheep occasionally twenty minutes, or even longer, will elapse before a solution 
of nitrite of potassium or sodium effects the characteristic change. The blood of the 
Dog, it must be remarked, is used in preference to that of the Ox and Sheep in the 
preparation of haemoglobin, because its blood-corpuscles when treated with Avater burst 
so much more readily than those of the Ox and Sheep. 
When it is desired to act upon blood with nitrite of amyl, the latter should be dis- 
solved in alcohol, and a few drops of the alcoholic solution added to the blood. 
Solutions of haemoglobin are immediately affected by the addition of nitrites. 
When blood has, through the addition of nitrites, assumed a chocolate-colour, the 
latter is immediately changed to a red on the addition of ammonia. 
The change in colour induced by nitrites in no way depends upon an alteration in the 
shape of the blood-corpuscles, as I have ascertained by numerous experiments. 
1 “ Note on the Action of Nitric Oxide, Nitrous Acid and Nitrites on Haemoglobin,” Proceedings of the 
Royal Society of Edinburgh, 1867, No. 73, p. 108. 
