178 ANNUAL OF SCIENTIFIC DISCOVERY. 



" I have yet to add some observations with regard to an adulteration 

 practised on the indigo. Each large indigo-chest contains a quantity of 

 dust, which is said to amount sometimes to eight or ten pounds. This 

 dust is an artificial product, composed of starch, or white lead, and 

 powdered indigo, and is put in the chest in order to increase its weight. 

 The finest Bengal indigo is to be preferred to the finest Java at the 

 same price, but Bengal No. 2 is nearly as good as No. 1, and its price 

 is one third less, while Bengal No. 3 is sold at half the price of No 1, 

 but is worth as dyeing material only one third as much." Jahrbuchfur 

 praktische Pharmacie. 



NEW METHOD FOR THE DETECTION OF IODINE. 



THE detection of small quantities of iodine is one of the most difficult 

 processes in chemistry, and any new and accurate mode will be at once 

 welcomed. We find in the Journal de Chemie Medicate for Sept., a 

 process by M. Thorel. It is a modified manner of using starch. Put 

 into a small phial 50 or 60 grams of the suspected liquor, or if it be a 

 solid body, diffuse it in a small quantity of water ; add six drops of 

 pure nitric acid and as much hydro-chloric acid ; a small piece of paper 

 is then to be covered with a rather liquid preparation of starch, and 

 placed at the mouth of the phial, which is to be heated. If the liquor 

 contains iodine, the paper will assume a violet blue tinge, of greater or 

 less intensity. The nitric acid sets the iodine free by decomposing the 

 iodides, if any exist ; the effect of the hydro-chloric acid is, that it is 

 substituted for the iodine by decomposing the iodate. If the paper 

 should not become colored at the moment of ebullition, the same quan- 

 tity of the two acids should be added, shaking the phial strongly. In 

 an instant the spots should appear, and the stratum of iodine will gra- 

 dually increase. It must not be immediately concluded that no iodine 

 is present, if no color appears, for it is separated with difficulty from 

 some bodies, such as molasses. In such cases a second operation must 

 be performed, adding to the liquor 10 to 20 centigrams of tartrate of 

 potash dissolved in a small proportion of water. Heat is to be applied 

 an instant before the addition of the acids, which, on this occasion, may 

 be used in the proportion of 8 to 10 drops of nitric acid, and 4 drops 

 of hydro-chloric acid. After this trial an opinion may be arrived at 

 with great certainty, as exceedingly minute quantities of iodine are thus 

 detected. 



A NEW TEST FOR ALBUMEN. 



WE find in the Comptes Rendus for Jan., an interesting paper 

 by M. Millon on a new test for albumen. He says that the 

 highly acid liquid obtained by dissolving mercury in its own weight 

 of nitric acid constitutes an extremely delicate reagent for albumen 

 and albuminous compounds. This mercurial solution communicates 

 to albuminous substances an intensely red color, by means of which 



