1918-19.] Reaction Velocity of Sodium Nitrite on Blood. 149 
XIII. — Some Conditions influencing the Reaction Velocity of 
Sodium Nitrite on Blood. By Professor C. R. Marshall. 
(MS. received May 5, 1919. Read May 5, 1919.) 
When a moderately strong solution of sodium nitrite is added to blood 
a change of colour almost immediately occurs, mainly owing to the forma- 
tion of methaemoglobin. The actual products of the reaction are not 
definitely known, and are not of importance to the present paper. The 
rapidity of the reaction is affected by the nature and concentration of the 
blood solution on the one hand, and by the concentration of the sodium 
nitrite solution on the other. Probably other factors, such as temperature, 
which has not been investigated, are of importance. The experiments 
referred to in this paper were made at room temperatures. 
Considerable variability was found in the reactivity of blood towards 
nitrites. The blood of different animals of the same species sometimes 
reacted differently quantitatively, and the same blood kept in the laboratory 
also tended to show slight differences from fresh blood. This was most 
noticeable when minimal concentrations of sodium nitrite were used. It 
was also found that different specimens of sodium nitrite gave different 
results ; the commercial sodium nitrite, which is decidedly alkaline, being 
much slower in effecting a change than the sodium nitrite employed 
medicinally. These preliminary observations were made with solutions 
of blood in a test-tube examined with a simple pocket spectroscope. In 
one series of experiments in which laked blood was diluted to contain 
definite concentrations of sodium nitrite, and examined every few seconds 
for the earliest appearance of the absorption band in the red, the results 
plotted in the lower curve in fig. 1 were obtained. 
It is necessary to state that the curve, although indicating generally 
the action of sodium nitrite, is only true for the particular specimen of 
blood and the conditions under which the experiment was made. For 
comparison the curve of a similar series of experiments with washed blood 
corpuscles in place of blood is given. The bend in the curve of the blood 
experiments with increasing dilutions of sodium nitrite, and the fact that 
discrepancies in the action of sodium nitrite more commonty occurred 
when whole defibrinated blood was used, suggested a possible influence 
of the serum ; and as the action and the variations were of interest in 
connection with another research, they were further investigated. 
