312 EXPEEIMENT STATION RECORD. [Vol.38 



and extract the carbonized mass with water. The insoluble portion is then 

 ignited separately and the ash added to the solution, which Is evaporated and 

 the residue gently heated. 



For tlie determination of potassium and sodium 5 gm. of the ash is repeatedly 

 extracted with boiling water and the extracts filtered into a 50t)-cc. flasli. 

 After thoroughly washing and cooling the solution to room temperature, it is 

 made up to volume. To 200 cc. of this solution 50 cc. of a saturated solution 

 of barium hydroxid is added in small amounts at a time with thorough 

 shaking. After allowing the precipitate to settle, phenolphthalein is added 

 and the solution treated with carbon dioxid until it is decolorized. Several 

 cubic centimeters of a saturated solution of ammonium carbonate are added, 

 the solution heated, filtered, the filtrate evaporated to dryness, and the residue 

 ignited. This residue is extracted with water, the solution filtered, and the 

 filtrates evaporated after the addition of hydrochloric acid. The residue of 

 chlorids thus obtained is ignited at a low temperature and weighed. Ammo- 

 nium carbonate solution may be used instead of the carbon dioxid for the 

 removal of the excess of barium hydroxid. The barium hydroxid removes the 

 carbonates, sulphates, and phosphates as insoluble barium salts and also the 

 magnesium and titaniiim. 



The potassium in the mixed chlorids is determined by precipitation with 

 chloroplatinic acid. The filtrate and washings obtained by washing the 

 chloroplatinates with a mixture consisting of 500 cc. of SO per cent alcohol 

 and 80 cc. of ether are evaporated to remove the alcohol and ether and boiled 

 with an excess of ammonium formate. The reduced platinum is separated by 

 filtration, the filtrate evaporated to dryness, and the residue ignited to expel 

 ammonium salts. The ignited residue is treated with a few drops of hydro- 

 chloric acid, evaporated, and the sodium chlorid thus obtained weighed after 

 gentle ignition. The amount of potassium may be checked by reducing the 

 potassium chloroplatinate with sodium formate and weighing the platinum 

 black obtained. 



The recovery of perchloric acid from residues obtained in the determina- 

 tion of potassium, A. VUktheim {Ckem. WeekbL, I4 {1911), No. ^3, pp. OSS- 

 OSS). — The author describes a procedure for the recovery of perchloric acid 

 from potassium perchlorate and from alcoholic filtrates containing the soluble 

 perchlorates of sodium, magnesium, and calcium. The latter are dried and the 

 residues used in the recovery. The procedure consists in treating the dry 

 material -with 97 per cent sulphuric acid and distilling at 170° C under a 

 reduced pressure of about 55 mm. The perchloric acid is collected in ice-cold 

 distilled water. Some chlorin and also sulphuric acid are carried over into 

 the distillate but are easily removed, the former by boiling the solution and 

 the latter by precipitation with barium chlorid. After the removal of these 

 substances the acid is made to the proper concentration required for analysis. 



The procedure has been found to be economical, especially in view of the 

 present scarcity and high price of perchloric acid. 



A rapid method for the determination of lime as calcium sulphate, L. G. 

 Willis and W. H. MacIntiee (Jour. Indus, and Engin. Chem., (1011), No. 12, 

 pp. lllJf-1116) . — The following modified procedure is described by the authors, 

 at the Tennessee Experiment Station : 



The calcium is carefully precipitated as oxalate, reprecipitated if necessary 

 where the magnesium content is appreciable, and the precipitate ignited in a 

 small platinum dish or platinum or porcelain crucible over a Bunsen flame or 

 in a muffle until the filter is completely incinerated. For each approximate 

 0.2 gm. of calcium carbonate enough of a 1 : 1 finely ground and dried mixture 



