CORRESPONDENCE 
7&3 
know that it acts as an irritant upon diseased surfaces. If it is 
too small, the solution don’t keep well. 
My opinion is, that a standard solution of medicinal H2 O2 
must answer the following tests : 
1. It should contain at least fifteen volumes of available 
oxygen. 
2. The quantity of free acids contained in 100 cubic centi¬ 
meters should require not less than 1 c. c. and not more than 
3 c. c. of normal volumetric soda solution, to be made neutral. 
Such e small quantity of free acid is not objectionable. 
3. It should not contain any soluble baryta salts. 
4. It must be free from sediment. 
It is to be noticed that the brands No. 7 and No. 12 are 
valueless. 
The brands No. 8 and No. 9 are not fit for medicinal uses, 
owing to the fact that they contain traces of soluble baryta salts. 
The brand No. 3 has a heavy sediment of sulphate of baryta; 
which maybe considered inert towards the system, but it is cer¬ 
tainly detrimental to the keeping qualities of this preparation. 
Brand No. 14, which is sold as a ten volume solution, 
is really twelve volumes, but it is too acid. Brand No. 5, which 
is sold as a fifteen volume solution, is really 16.55 volumes, viz.: 
About ten per cent, above the standard. 
The brand No. 2, which is sold without any mention of vol¬ 
ume, is really a 27.35 volume solution, viz.: Ninety per cent, 
above the standard. 
None of the other brands come up to the standard, but on 
the contrary they run from 35 to 55 per cent, below. 
CORRESPONDENCE. 
DR. SALMON REPLIES. 
Editor American Veterinary Review. 
Dear Sir :—In a letter published in the December number 
of the Review, Dr. Schwarzkopf .does me the honor to use my 
