10 EXPERIMENT STATION EECOED. 



method v/iiich is claimed to have definite advantages in regard to accuracy and 

 time but can not be used for solutions containing heavy metals ; 



The dilute, slightly acid (HCl') solution containing the sulphate ion is 

 brought to active boiling, and to it is added an excess of barium chlorid (200 

 gm. of water-free salt in 1 liter), corresponding to 50 per cent of the sulphate 

 present. The mixture is allowed to stand until the next day, the supernatant 

 fluid poured off through a filter, and the filtrate thrown away. The residue is 

 then boiled for J hour with 125 cc. water which has been slightly acidified with 

 nitric acid, and allowed to settle. The supernatant fluid is jiassed through the 

 original filter and the residue repeatedly subjected to the same treatment until 

 the precipitate is free of chlorin. 



The wash waters in each instance are reserved, and after the completion of 

 the process the filter is punctured and the portion of the precipitate on the 

 filter is washed into the beaker containing them. The wash waters are then 

 concentrated to a bulk of 200 cc, and to them is added 2 cc. of a saturated 

 barium nitrate solution, cooled, and the resulting precipitate allowed to settle 

 I hour. After this the precipitate is brought on the filter and washed, the 

 major precipitate is added, and the whole dried at 100° C. The precipitate is 

 then separated from the filter and both filters employed in the process are 

 incinerated in a porcelain crucible. The ash is added to the precipitate, heated 

 with a small flame, cooled, and weighed. 



A volumetric naethod of determining iodid in the presence of chlorid, 

 bromid, or free iodin, W. C. Bray and G. M. J. Mackay {Jour. Amer. Chem. 

 ISoc, 32 {1910), Xo. 10, pp. 1193-120J/). — " In this article a method of determin- 

 ing iodid in aqueous solution is described, which depends uix)n the oxidation of 

 the iodid ... by permanganate, the removal of the liberated iodin by carbon 

 tetrachlorid, and the titration of this iodin with a standard sodium thiosulphate 

 solution." 



A note in regard to the Kjeldahl method for determining nitrogen, B. F. 

 Harrison and P. A. W. Self {Pharni. Jour. [Lon(lon'\, Jf. ser., 31 {1910), No. 

 2J,37, p. 4; ahs. in Chem. Ztg., 34 {1910), No. 100, Repert., p. Jf09).— The authors 

 draw attention to the fact that when distilling off the digested fluid a portion 

 of the alkaline fluid is carried over with the vapors into the distillate, thus 

 bringing an error in the final results. 



A new method for estimating phosphoric acid, G. F. W. Martin {Abs. in 

 Ztschr. Angew. Chem., 24 {1911), No. //, p. 173). — The phosphoric acid is pre- 

 cipitated as ammonium phosphomolybdate. After washing with distilled water 

 the precipitate is dissolved in an excess of potassium hydrate and the am- 

 monia contained in the mixture distilled over into a measured amount of normal 

 acid (102 parts of ammonia =142 parts of phosphoric acid). 



Titrametric determination of citrate-soluble phosphoric acid, L. Wtjyts 

 {Ann. Phann., 1910, p. 337; ahs. in Ann. Falsif., 4 {1911). No. 27, p. ^6).— The 

 method is as follows : 



To 10 cc. of a 2 per cent citrate-phosiihate solution add a few drops of hy- 

 drochloric acid, evaporate in a small porcelain dish, add 3 or 4 drops of 

 nitric acid and a few cubic centimeters of water. Then add 10 cc. of strong 

 nitric acid (speciflc gravity 1.4), 15 cc. of ammonia, boil for from 2 to 3 min- 

 utes, cool, add 25 cc. of ammonium molybdate, and stir with a glass rod. De- 

 cant on the filter with cold water; 5 to 6 washings are usually sutficient. 

 Dissolve the precipitate in potassium hydrate solution, controlling this with 

 phenolphthalein, add 50 cc. of water, and titrate back with a normal solution 

 of sulphuric acid. The number of cubic centimeters of potassium hydrate solu- 

 tion utilized directly represents the percentage of phosphoric acid present. 



