P it nt ei le 
ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 171 
It is well known that most of these salvarsan compounds 
teteriorate and become more toxic on exposure to air. Thus within 
an hour the toxicity of neo-salvarsan increases 3 to 6 fold, the 
arsalytes within 24 hours increase 2} times in toxicity, and the same 
applies to the metallic salvarsan compounds. Colloidal metal sols 
(lo not become toxic, even on prolonged exposure. 
Hexamino-salvarsan in the moderate dose of 0-4 grm. has pro- 
duced grave symptoms and even fatal results which led to its 
discontinuance. Gold and platinum salvarsan possess too great a 
toxicity for therapeutic use in man. Silver salvarsan, on the 
contrary, is 2 to 3 times as potent as old salvarsan and it is by far the 
most active form of salvarsan for destroying the spirochetes in 
rabbit syphilis and in curing the lesions. It has likewise been used 
with excellent results in man in doses of 0'2 to 0-4 grm. Kolle does 
not state the exact chemical constitution of this substance, but it is 
highly probable- that much of the silver is in a colloidal state, 
especially as he found that colloidal silver (collargol) alone in doses 
of 0°03 grms. per kilo caused the rapid disappearance of spirochetes 
in the rabbit. 
Colloids and Physiological Ketracts. 
The remarkable results which have followed the administration 
of certain physiological extracts (thyroid, pituitary, ete.) appear 
to be largely due to the presence, in them, of sulphur or an 
equivalent element in a suitable form. 
The substitution of carefully prepared colloidal sols for such 
extracts largely avoids the risks of irregular and uncertain com- 
position which inevitably accompany the use of such extracts. 
. Colloids in Veterinary Practice. 
Colloidal silver and sulphur have yielded excellent results in 
veterinary practice, the former in the treatment of swellings, sprains, 
bruises, wounds, sores, rheumatism, thrush in the feet, fistula, various 
skin diseases and inflammation of the eyes, and the latter for cases 
where a deficiency of sulphur is indicated. 
The Limitations of Colloids. 
The selection and use of colloidal sols requires the same care and 
skill as the administration of any other remedies, but with the great 
advantage of being made specific and rational rather than empiric. 
A word of warning may be expressed as to the use of unstable 
colloids in medicine. A. number of colloidal preparations—particu- 
larly of silver and iodine—has been placed on the market which 
have not been properly stabilised. The use of these preparations 
has been accompanied by disappointing results, as it is essential (as 
previously mentioned) that the colloids exhibited should be stable 
in the presence of serum and saline solutions. 
The failure of numerous colloidal sols of German (and some of 
British) origin created, in some minds, a prejudice against all colloidal 
remedies. The failures have been found, in every case examined, to 
have been wholly due to the method of preparation, Thus, it has 
