Intelligence and Miscellaneous Articles. 395 



3rd. Lastly, the third process, which is that proposed by M. Fehling, 

 is based on the following fact : when a mixture of an alkaline chlo- 

 ride and bromide is perfectly precipitated by nitrate of silver, the 

 first portions of the precipitate contain all the bromine which the 

 solution contained. 



This process, therefore, admits of concentrating the bromine, and 

 employing such a quantity of nitrate of silver as is insufficient to 

 precipitate the whole of the chlorine ; and as the object is merely that 

 of obtaining a compound of bromide and chloride very rich in bro- 

 mide, the first process becomes readily applicable without any risk 

 of serious error. 



The silver precipitate ought to be well washed, and in order to 

 decompose it by chlorine, it is to be fused, a quantity being intro- 

 duced into a tube with a bulb, which is to be heated by a spirit-lamp. 

 — Journ. de Pharm. et de Chim., Septembre, 1849. 



DETECTION OF SMALL QUANTITIES OF IODINE. 

 BY M. L. THOREL. 



The method employed by the author for this purpose is the fol- 

 lowing, and is merely a modified method of using starch. Put into 

 a small vial fifty or sixty grammes 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 the same quantity of hydrochloric acid ; a small 

 piece of paper is then to be covered with a rather liquid prepara- 

 tion of starch and placed at the mouth of the vial, which is to be 

 heated. If the liquor contains iodine, either in the state of iodide or 

 iodate, the paper will assume a violet blue of greater or less inten- 

 sity. The nitric acid sets the iodine free by decomposing the iodides, 

 if any exist ; the effect of the hydrochloric acid is, that it is substi- 

 tuted for the iodine, by decomposing the iodate, if it should be pre- 

 sent. 



If the paper should not become coloured at the moment of ebul- 

 lition, the same quantity of the two acids should be added, shaking 

 the vial strongly. In an instant, the spots should appear, and the 

 stratum of iodine will gradually increase. It must not be immedi- 

 ately concluded that no iodine is present if no colour appears, for it 

 is separated with difficulty from certain bodies, as happens with mo- 

 lasses. In such cases a second operation must be performed, adding 

 to the liquor ten to twenty centigrammes of tartrate of potash dis- 

 solved in a small proportion of water. Heat is to be applied an in- 

 stant before the addition of the acids, which on this occasion may 

 be used in the proportion of eight to ten drops of nitric acid, and 

 four drops of hydrochloric acid. After this trial an opinion may be 

 arrived at with great certainty. 



By operating in this manner, the presence of iodine may be de- 

 tected in a mixture which contains only three to four milligrammes. 

 With a mixture of twenty milligrammes of iodine and 200 grammes 

 of salt, very intense spots may be obtained. — Journ. de Chem. Med., 

 Septembre 1849. 



