
1905.| in Gastric Contents in Malignant Disease of Organs. 147 
method and the Mérner-Sjoqvist method it would be necessary to know the 
amount of organic bases present in order to obtain accurate results. The figures 
are given as of interest in showing that organic bases in combination with inorganic 
acid must be present in the stomach contents in these cases, and on account of 
the light they shed on the high result in Cases XI, XVI, and XVII with the 
Morner-Sjoqvist method. 
The presence under the pathological conditions of such compounds of organic 
bases with inorganic acid is in itself of high interest, and requires further 
investigation. 
Determination of the Concentration of Hydrogen Lons by the Velocity of Inversion of 
Methyl-A cetate. 
A determination of the concentration of the hydrogen ions in the gastric 
contents gives not only one of the best means of determining the character of the 
acid present, but furnishes the best guide to the real degree of acidity in the fluid. 
The figures obtained by titration to the neutral point (or by a gravimetric 
method such as that of Morner-Sjéqvist) give only what might be termed the 
total or potential acidity or alkalinity of a solution, and not the active acidity 
or alkalinity at any given moment. Thus, a deci-normal solution of any organic 
acid, such as acetic, lactic, or butyric, requires for titration to neutrality with a 
sensitive indicator such as phenol-phthaléin, just as much of a deci-normal alkali 
solution as does a deci-normal solution of an inorganic acid such as hydrochloric, 
sulphuric, or nitric, and, again, a solution of caustic alkali requires no more acid of 
any nature for neutralisation than does a solution of equi-normal strength of 
alkaline carbonate, or of an alkaloid. Yet we clearly recognise by the effects of 
such acids and alkalies that the state of affairs in such solutions are quite different, 
and that in popular language we have weak and strong acids and alkalies. 
The explanation lies in the fact that only a certain fraction of the acid or alkali 
in the solution is effective at any given concentration, and the value of the effective 
fraction varies within wide limits with the nature of the particular acid or alkali in 
question. 
When an acid is dissolved in water it becomes partially ionised into a hydrogen 
ion, and an ion represented by the remainder of the formula of the particular acid, 
while the remaining un-ionised portion maintains a balance or equilibrium in the 
solution, and is inert as regards acid properties, the degree of acid activity of the 
solution depending entirely upon the concentration of the hydrogen ions. 
Similarly, when an alkali is dissolved, it becomes partially ionised into a 
hydroxyl ion, and another ion, dependent in constitution upon the alkali in 
question ; and in part remains un-ionised. Here the hydroxyl ion, by its concen- 
tration determines the degree of activity as an alkali, just as in the case of the 
acid, the concentration of the hydrogen ion determines the acidity. 
_ Taking, as examples, hydrochloric acid and potassium hydroxide, the condition 
. of things when solution takes place may be represented by the equations :— 
+ Be 
(m+n)HCl = mHCl+ nH +nCl 
(m+n)KOH = mKOH + nk +nOH 
