1865.] Chemistry. 6G7 



Fresenius has made a series of experiments on the determination 

 of phosphoric acid as phosphoniolybdate of ammonia.* He finds, in 

 effect, that the results are sufficiently correct in a nitric acid solution ; 

 but hydrochloric acid, even when very dilute, somewhat interferes 

 with the precipitation. 



We may here notice very shortly a method of elementary organic 

 analysis, proposed by Dr. Ladenburg,-j- to supersede in some cases 

 Liebig's combustion process. The author encloses a weighed amount 

 of the substance to be analyzed in a small glass bulb, which he places 

 in a stout tube containing a weighed quantity of iodate of silver and 

 some monohydrated sulphuric acid. This tube being sealed, the bulb 

 is broken by agitation and the tube heated, whereupon the organic 

 substance is oxidized at the expense of the oxygen of the iodic acid. 

 At the end of the operation the tube is weighed ; it is then opened, 

 and the carbonic acid pumped out ; the loss of weight gives the 

 amount of the acid formed. The free iodine is then estimated in the 

 sulphuric acid solution by Bunsen's method ; and thus the amount of 

 oxygen required for the oxidation is ascertained. This method, it 

 will be seen, is specially applicable for the volatile hydro-carbons. 



Mr. Ullgren has contributed to the 'Journal of the Chemical 

 Society'! a method of estimating very closely the amount of blue 

 colouring matter in indigo. It is a volumetric method based on the 

 fact that ferricyanide of potassium in the presence of a free alkali, 

 destroys the indigotin and produces colourless isatin. The solution 

 of ferricyanide he employs contains 2*5115 grammes of the salt in 

 a litre, consequently 2 c.c. change 1 milligramme of indigotin into 

 isatin. To ensure accuracy in the determination, the quantity of 

 sulphuric acid added to the indigo solution should not be too great, 

 and the temperature should not exceed 50° ; the indigo solution must 

 be very dilute ; and the solution must be made strongly alkaline by 

 carbonate of soda. The operation may be regarded as complete when 

 the bluish-green solution assumes a grey-yellow appearance ; or when 

 every tint of blue has disappeared. 



As a ready means of distinguishing between bismuth and lead, 

 we may give a test described by Nickles, who shows that the chlo- 

 rothallate of ammonia precipitates bismuth, but does not precipitate 

 lead. 



In connection with organic chemistry, we notice the researches of 

 M. Fremy on the green colouring matter of leaves.§ The author 

 shows that chlorophyll yields two distinct colouring matters which 

 may not, however, primarily exist in that body. "When an alcoholic 

 solution of chlorophyll is boiled with hydrate of baryta, a yellow body, 

 phylloxanthine, is precipitated along with a barytic salt of phyllocy- 

 anic acid. The former may be dissolved out by alcohol, and obtained 

 in reddish-yellow crystals by evaporating the solution. The barytic 

 salt mentioned when decomposed by sulphuric acid, gives a solution 



* ' Zeitschrift fur Analyt. Chem.,' Bd. iii., p. 446. 

 t ' Annalen der Chem. und Pkarin.,' Bd. lix. s. 1. 

 % August, 1865. § Comptes Reudus, t. lxi. p. 188. 



VOL. II. 2 z 



