1888.] Haycraft and Williamson on Alkalinity of Blood. 397 
on the surface. This he removed by the blade of a knife or by a 
stream of water, when a blue stain, the reaction of the plasma, was 
exposed to view. Klihne, on the same principle, allowed the plasma 
of blood to diffuse through the pores of parchment paper, and tested 
it with litmus. As far as I am aware, only one method has been 
introduced, by means of which the amount of alkalinity may be 
determined.* This is the very excellent method of Zuntz, which 
has been modified by subsequent observers. He showed that 
carefully-prepared and well-glazed litmus could be used to replace 
the plates of Liebreich; this has been subsequently verified by 
Schafer. In his quantitative researches he added to a given 
quantity of blood sufficient standard phosphoric acid solution to 
neutralise it, testing with glazed litmus paper, the alkalinity being 
proportional to the quantity of phosphoric acid added. This method 
in the hands of a careful observer is calculated to give excellent 
results. Inasmuch, however, as a considerable quantity of blood is 
required for a single estimation, one is unable to use it in many 
researches, nor can it be applied for clinical purposes. My former 
demonstrator, Dr Williamson, and I have endeavoured to discover 
some method by means of which the quantity of alkali present may be 
determined in a single drop of blood. To begin with, we examined 
several colour tests, comparing them in each case with litmus. 
Some of these, newly introduced into analytical work, are for many 
purposes more sensitive than litmus. We found, however, after 
many trials, that none gave as good a reaction with blood-plasma as 
litmus. Amongst other substances, we experimented with cochineal, 
aurin, eosin, turmeric, alizarine, and phenolphthalein. The alkalinity 
of the blood is due chiefly to the bicarbonate and phosphate of 
sodium. The reaction of these substances we found was given 
better by litmus than by any other test tliat we employed. Phenol- 
phthalein, so useful for many purposes, gives no reaction whatsoever 
with ordinary blood-serum. We were, however, much impressed by 
the great sensitiveness of litmus itself, which gives a reaction with 
blood-serum largely diluted with water. 
It is possible to make an acid litmus paper, which will give a 
reaction with an alkaline solution, provided only the alkali is strong 
* Zur Kentniss des Stoffwechsels im Blute Cent, fur die Med. Wiss., No. 51, 
1867. 
