200 ACTION OF CERTAIN CHEMICAL REAGENTS. 
6. That no other chloride besides sal ammoniac can de- 
compose iodide of potassium at ordinary temperatures and 
in contact with moist air ; but may at a high temperature. 
7. Finally, that it is advantageous for the practitioner to 
employ a mixture of iodide of potassium and sal ammoniac, 
as an external application, when the object is to develope suc- 
cessive portions of iodine in small quantities, and for a long 
time, as the disengagement of iodine will continue without 
interruption for several months. 
Journ. de Pharm. 
ART. XL, — ON THE LIMIT TO THE ACTION OF CERTAIN 
CHEMICAL REAGENTS. 
Mr. P. Hastings, having examined the action of certain 
chemical reagents, has given the following statement of the 
results. 
I. The sensibility of starch as a reagent for iodine. 
Iodide of potassium slightly acidulated with nitro-muriatic 
acid, tested by a diluted solution of starch, gave the following 
results. 
1. Containing l-500dth iodine gave a black precipitate, 
the upper surface brownish yellow. 
2. Containing l-1000dth iodine gave nearly the same 
color. 
3. Containing l-2000dth iodine, gave the precipitate the 
same color, but the solution slightly colored. 
4. Containing l-3000dth iodine, precipitate bluish black, 
the solution nearly clear. 
5 and 6. Containing l-4000dth to l-5000dth iodine, pre- 
cipitate bluish black, the solution quite clear. 
7 to 11. Containing l-10,000dth to l-40,000dth iodine, 
very dark blue. 
