CHEMISTRY. 229 



solved and acidulated with chlorliydric acid, a distinct yellow pre- 

 cipitate with sulplmretted hydrogen. 



Tiie arsenic is undoubtedly derived from the sulphuric acid 

 used in converting the common salt into sulphate of sodium, as 

 the pyrites used in the manufacture of sulphuric acid often contain 

 arsenic in notable quantities and are rarely entirely free from it. 



Test for Prussian Blue. — Nickles found that Prussian blue 

 might be distinguished from the blue of indigo or aniline by 

 means of. fluoride of potassium, which bleaches the former and is 

 without effect on the other two. — Journ. Frank. Inst. 



Test for Hydrocyanic Acid. — Schonbein moistens filtering 

 paper with fresh tincture of guiacum, containing 3 or 4 parts of 

 resin, and, after drying, moistens the paper with a solution con- 

 taining one quarter of one per cent, of sulphate of copper. This 

 paper is instantly rendered blue in the atmosphere of a 20-litre 

 vessel containing one drop of dilute hydroc3"anic acid of one per 

 cent. — Schw. Wochenscrf, f. Pharm. 



Binoxide of Hydrogen as Test for Prussic Acid in Blood, which 

 was proposed by Schonbein and again by Buchner, requires great 

 care in its application, according to Dr. Huizinga, inasmuch as 

 any acid reaction of blood, produced by the usual mineral or 

 organic acids, causes the same brown color. At the same time it 

 must be noted that the spectroscopic reactions for the color pro- 

 duced by prussic acid or cyanides are quite distinct, and so are 

 the chemical tests for them. — Fresenius, Zeitsch.f Analy. Chemie. 



Beagent for Alkaloids. — M. Marme proposes the use of the 

 double iodide of cadmium and potassium as a reagent for alka- 

 loids. This compound precipitates the following alkaloids from 

 very dilute solutions mixed with sulphuric acid : Nicotine, 

 conicine, piperine, morphia, codeia, thebaine, narcotine, narceine, 

 quinine, quinidine, cinchonine, strychnine, brucine, veratrine, 

 berberine, atropine, aconitine, and some others. The precipi- 

 tates are white and flocculent, but for the most part become 

 crystalline. Quinine and strychnine, diluted with 10,000 parts of 

 water, are entirely precipitated. These precipitates are insoluble 

 in ether, soluble in alcohol, slightly soluble in water, and soluble 

 in an excess of the double iodide. 



This reagent does not precipitate glycosides. — Chem. Neics. 



On the Estimation of the Iodine of Commerce by Volumetric 

 Analysis. — M. Bobierre dissolves a weighed quantity of the 

 iodine, the true value of which has to be estimated, in a concen- 

 trated solution of iodide of potassium ; the" solution is diluted to 

 100 c.c, and is dropped into an alkaline solution of arsenious 

 acid of known strength. Instead of using starch-water as a 

 means of recognizinjr the end of the reaction, the author adds a 

 few cubic centimetres of benzol to the solution of arsenious acid, 

 and ceases to add more of the solution of iodine as soon as the 

 former solution becomes rose-colored. The arsenical solution 

 is made by Aveighing off 49.95 grms. of arsenious acid, and 14.5 

 grms. of crystallized carbonate of sodium, and dissolving these in 

 one litre of water, representing 12.G88 grms. of iodine to the 



20 



