504 EXPEEIMENT STATION RECOKD. 



aqueous ammonia (22° B.) with sulpliur dioxid — ttie liquid is lieated to about 

 80° C. and, upon the appearance of a crystalline precipitate, 20 cc. of am- 

 monia solution (22° B.) are added and the mixture is well stirred. The calcium 

 sulphite, precipitated (in crystalline form) in accordance with the equations: 

 CaCl2+3NH4HS03+NH»=CaSaO,+2NH4Cl+(NH4)2SOB+H20, and CaS.Oo+ 

 2NH3+H=0=CaS03+(NH4)2SOs, is allowed to settle for an hour and is theu 

 filtered off, washed with hot, slightly ammoniacal water, dried, calcined in a 

 muffle, and weighed as calcinm sulphate; before incineration, the filter paper is 

 moistened with a saturated solution of ammonium sulphate containing free 

 sulphuric acid to prevent the formation of calcium sulphid. After the complete 

 expulsion of the free and combined sulphurous acid from the filtrate, the mag- 

 nesium is determined by precipitation with sodium phosphate in the usual 

 manner." 



The method requires about 3 hours for each determination of calcium. Zinc, 

 niclvel. and cobalt when present do not influence the process. See also a pre- 

 vious note by Hinds (E. S. R., 2G. p. 21). 



A short m.ethod for the determ^ination of soluble arsenic in commercial 

 lead arsenates, B. E. Curry and T. O. Smith {Jour. Indus, and Engin. Chcin., 

 Jf (1912), No. 3, pp. 198-201). — The official method for soluble arsenic oxid re- 

 quii'es 10 to 11 days, so that to economize time the following method, which 

 only takes about 2 days in all and will give results as total soluble arsenic, was 

 devised : 



An amount of moist commercial arsenate, corresponding to 2 gm. of dry sub- 

 stance, is placed in a flask with 500 cc. of water and agitated continuously in 

 a thermostat at 20° C. for IS hours by means of a hot-air enguie. The mixture 

 is then filtered and a small portion of the filtrate tested for arsenious oxid. 

 If pi'esent, 200 cc. of filtrate is taken, some bicarbonate of soda and starch 

 added, and titrated with a standard iodin solution. The solution is then treated 

 with 5 cc. of sulphuric acid and 1 gm. of potassium iodid, evaporated to a bulk 

 of from 40 to 50 cc, and then diluted to 150 cc. with water. If an excess of 

 iodin is present, it may be removed by the addition of twentieth-normal sodium 

 thiosulphate solution until no yellow color remains. The solution is now ren- 

 dered slightly alkaline with sodium hydrate, then acid with dilute sulphuric 

 acid, and alkaline again witli sodium bicarbonate. The arsenite is then titrated 

 with iodin solution, employing starch as the indicator. The solubility of lead 

 arsenite for this procedure is less than it is in the official method, i. e., 0.151 

 with the former and 0.(305 with the latter method. By deducting 0.151 from tlie 

 results obtained with the method described the percentage of total soluble 

 arsenic is obtained. The figures agree well with the oflicial method when the 

 results of both methods are corrected. 



Determination of saltpeter in meat, J. Tillmans and A. Splittgerbeb 

 (Ztschr. Vntcrsuch. XaJir. iu Gcnussmtl., 23 {1912), No. 2, pp. 40-56; abs. in 

 Ztschr. Angcw. Chcm., 25 {1912), No. 11, p. 8.52).— Tests made with the brucin- 

 sulphuric acid method and the diphenylamin sulphuric acid method with com- 

 mercial samples and samples prepared with known potassium nitrate content 

 show that both methods are sufficiently accurate for ordinary work. Where 

 exact results are required the Schlosswig-Wagner method must be used. The 

 literature is discussed. 



Detection of alum in flour and bread, W. Lenz {Apoth. Ztg., 26 {1911), 

 No. 66, pp. 687-689; ahs. in Cliem. Ztg., 35 {1911), No. 130, Report., p. 541).— 

 The method is as follows: Two gm. of flour is mixed in a test tube with 3 cc. 

 of water and 1 cc. of a 1 per cent solution of hematoxylin in 50 per cent alcohol, 

 and then thoroughly shaken with 10 cc. of a saturated solution of sodium 



