1919] AGRICULTURAL CHEMISTRY AGROTECHNY. 313 



The choice of indicators for the acidimetric determination of boric acid, 

 J. Pbeschek (Ztschr. Untersuch. Nahr. u. Genussmtl, 36 (1918), No. 11-12, pp. 

 283-286). — Sources of error in the use of various indicators in the acidimetric 

 determination of boric acid are discussal, and phenolphthalein is recommended 

 as giving the most accurate results. 



The alkalimetric determination of small amounts of magnesium, P. L. Hiu- 

 BAKD (Jowr. //((/M.S'. and Engin. Chem., 11 {1919), No. 8, pp. 153, 75//).— Certain 

 modifications in the Bruclcmiller process for determining magnesium by titra- 

 tion of annuonium magnesium phosphate (E. S. II., 37, p. 412) have been 

 introduced by the author in an application of the method to the determina- 

 tion of magnesium in soil extracts. The principal changes consist in the 

 use of the Gooch crucible for filtration, of neutralized alcohol followed by a 

 water solution of ammonium magnesium phosphate for washing, and of methyl 

 red instead of methyl orange as an indicator. The method as modified is 

 said to be exact for the estimation of quantities of magnesium of 5 mg. 

 or less dowti to 0.1 mg. 



Standards of purity for food products ( U. S. Dcpt. Agr., Off. Sec. Circ. 136 

 {1919), pp. 22). — This circular contains the definitions and standards for food 

 products published in the form of Food Inspection Decisions since Circular 19 

 (E. S. R., 18, p. 459), which it supersedes, and those originally published in 

 that circular which have not been superseded by such decisions. 



Analyses of flours for the determination of the percentage extraction, O. 

 Pbandi and F. Perracini {Stas. Sper. Agr. Ital, 50 {1917), No. 6-8, pp. 391-393; 

 abs. in Chem. Abs., 13 {1919), No. 12, p. 1349). — To determine the percentage of 

 extraction of a flour the authoi'S state that, in addition to the microscopic and 

 organoleptic examination, the test should include determinations of nitro- 

 gen, ether extract, cellulose, and ash. The formation of furfural from flour by 

 heating with hydrochloric acid and its subsequent determination as phloro- 

 glucid are recommended as furnishing additional evidence in doubtful cases. 

 The results obtained by the authors with this determination, using the Tollens- 

 Kriiger method on 400 cc. of the distillate and calculating to the dry basis, are 

 as follows : Flour of 80 per cent extraction, minimum 3.1 per cent, maximum 

 3.31, average 3.25 ; 85 per cent extraction, minimum 3.81, maximinn 4.G1, aver- 

 age 4.09 ; and 90 per cent extraction, minimum 6.7, maximum 7.18, average 6.95 

 per cent. 



The milling grade of rye flour, J. Gerum {Ztschr. TJntersuch. Nahr. u. 

 Genussmtl, 31 {1916), No. 6, pp. 176-180). — The author considers the determi- 

 nation of total nonstarches to be the best method for judging the milling grade 

 of rye flour. Starches are determined by the method of Lehmann and Scho- 

 walter (E. H. 11., 28, p. 807), 30 minutes heating with alcoholic potassium 

 liydroxid being sufficient. The nonstarches are estimated by difference. The 

 results are reported of the application of this method to the examination of 

 several samples of rye flour. 



The marc content of sugar beets and its determination, H. Claassen 

 {Ztschr. Ver. Deut. Zuckerindus., 1916, No. 723, II, pp. 359-370; abs. in Chem. 

 Abs., 11 {1917), No. 9, p. 1330). — A method of determining the marc content of 

 sugar beets which is .said to give very concordant re.sults is described as follows: 

 Twenty-five gm. of the shredded beet pulp is placed in a beaker having a 

 mark at 400 cc. The beaker is filled to the mark with boiling water and the 

 mixture digested for 2 minutes. The solution is poured off as completely as 

 possible and the process repeated three times. The marc is then transferred to 

 a weighed filter or Gooch crucible, washed with a little alcohol, dried for from 

 6 to 8 hours at 105 to 110° C, and weighed. To determine the solubility of the 



