[ 529 ] 

 LXXVII. Intelligence and Miscellaneous Aiticles. 



ON IODINE IN COMMERCIAL NITRIC ACID. 

 1\/I LEMBERT observes, that among the substances which render 

 -'■'-'■ * the nitric acid of commerce impure, there is one which has not 

 been hitherto suspected, but which is not unimportant, namely, io- 

 dine. The following are the means by which its presence was de- 

 monstrated, for the first time, in purifying nitric acid : in order to ob- 

 tain pure concentrated nitric acid, A'l. Lembert takes the nitric acid 

 of commerce, adds nitrate of silver to it, and allows it to remain for 

 some days ; then pours off the clear acid, adds an equal weight of con- 

 centrated sulphuric acid, and distils the mixture. On one occasion 

 in concentrating the sulphuric acid remaining in the retort, and 

 when this was nearly completed, violet vapours appeared, and after- 

 wards crystals of iodine were formed in the tube used as a refrige- 

 ratory. 



Saturate nitric acid containing iodine with potash or soda, and to 

 the solution add a little clear solution of starch, and a few drops of 

 sulphuric acid, taking care not to add it till after it has been proved 

 that the quantity already used wa5 insufficient to elFect the colora- 

 tion. The i)resence of iodine will be thus determined by the blue 

 or purjjle colour which the liquid will assume. 



Reflecting on the origin of the iodine in the nitric acid, it was 

 natural, says M. Lembert, to tliink that it was derived from the ni- 

 trate of soda used in preparing the acid ; he consequently examined 

 this salt by adding to a solution of it a small quantity of solution of 

 starch, and then of sulphuric acid, and the colour indicative of the 

 presence of iodine was produced. 



M. Lembert remarks, that 1st, concentrated nitric acid, that is 

 to say, of specific gravity about 14, contains iodine, while the weaker 

 acid, or of specific gravity about 1'3, does not : 'indly, neither cldo- 

 rine nor sulphurous acid indicates the presence of iodine either in 

 natural nitrate of soda or the neutralized acid. — Journal de Pkartn. 

 et de Chimie, Avril 1842. 



ON THE PRKPARATION OF HYDUOUROMIC AND HYDRIODIC ACID. 

 BY M. MELLON. 



The author obtains hydrobromic acid by introducing into a flask 

 about 230 grains of bromide of potassium and a little water ; he then 

 adds about 380 grains of bromine and 30 grains of phosphorus in small 

 pieces ; he afterwards adapts a conducting tube to the neck of the 

 flask ; in a short time reaction commences, and it may become so 

 strong as to render it necessary to immerse the flask in cold water. 

 When the action diminishes, heat is to be gently applied by a spirit- 

 ]um|) ; the residue is a mixture of unaltered bromine and j)hospliate 

 of potash ; the gas liberated is derived from two diflfcrent sources ; it 

 results from the formation of bromide of ))hospIu)rus, wliich water 

 decomposes into hydrobromic and j)hosphoric acids ; and secondly, 

 from the action of the jihosphoric acid thus formed on the bromide 

 of pota.ssium. 



/''////. Mag. S. 3. Vol. 20. No. l.'i.S. June 1842. 2 N 



