1896 | TOXIC ACTION OF DISSOLVED SALTS 85 
as dilution increases, so that, as was pointed out above in the 
case of sodium chloride, dissociation is practically complete 
when an equivalent in grams is dissolved in 1000 liters of water. 
Hydrochloric acid dissociates into H ions and Clions. A 
dilute solution of sodium chloride and one of hydrochloric acid 
both contain Cl ions. Their difference, then, is due to the fact 
that the former solution contains H ions, whereas the latter con- 
tains Naions. To this difference are to be ascribed all the dif- 
ferences of properties that the two solutions possess. Solutions 
of all acids contain H ions, solutions of all chlorides contain Cl 
ions, those of sulphates SO, ions, those of nitrates NO, ions. 
Salts of copper in solution yield Cu ions, those of lead Pb ions, 
etc. In general, if BA represent the formula of a salt, B repre- 
senting the basic radical and A the acid radical, then in dilute 
aqueous solutions this compound is to a greater or less extent 
dissociated into the ions B* and A-, and, as stated, all the 
physical and chemical properties that such a solution possesses 
are due to the properties of the ions together with the proper- 
ties of the undissociated molecules present. 
THE PHYSIOLOGICAL ACTION OF DILUTE SOLUTIONS. 
It has always been taken as axiomatic that the physiological 
action of any substance is due to its chemical character. Now 
if, in the case of the solutions in question, all the chemical and physical 
properties are due to the properties of the ions plus those of the undisso- 
ctated molecules it contains, it seems very probable that the physiologt- 
cal effect produced by such solutions is also due to these. This thought, 
simple as it is, has to our knowledge never before been expressed. 
Many investigations on the physiological action of aqueous 
Solutions of salts on bacteria and higher forms of plant life as 
well as on‘animals have been made. The strengths of the solu- 
tions with which these experiments were performed have always 
been €xpressed in per cent. by weight; thus chemically equiva- 
lent quantities (7. e. molecular quantities) of the different sub- 
stances were not compared, and it is probably for this reason 
that general considerations have entirely escaped observation. 
