412 EXPERIMENT STATION RECORD. 



"As ammonia is estimated at the same time, this must be estimated separately 

 in another portion of the extract, and an allowance made for its quantity. The 

 details of the process are: One hundred cc. of the extract is treated with 10 cc. 

 of normal hydrochloric acid, 10 cc. of a 10 per cent silicotungstic acid solution, 

 and 10 cc. of a 3.1 per cent quinin hydrochlorid solution, shaken, submitted to 

 centrifugal action and filtered. The filtrate is shaken with animal charcoal, 

 again filtered, and 78 cc. of the filtrate is treated with 1 gm. of barium chlorid, 

 then rendered alkaline with potassium hydroxid solution, diluted to 100 cc, 

 and filtered. Twenty-five cc. of this filtrate (equivalent to 15 cc. of the original 

 extract) is acidified with tenth-normal hydrochloric acid, 1 drop of a satu- 

 rated p-nitrophenol solution is added, and the solution exactly neutralized 

 with tenth-normal potassium hydroxid solution. Fifteen cc. of neutral for- 

 maldehyde solution is now added, and the amino acids are titrated with tenth- 

 normal potassium hydroxid solution, using phenolphthalein as indicator. Let 

 N denote the number of cubic centimeters required for the titration ; the am- 

 monia is then estimated by distilling a further quantity of 50 cc. of the extract 

 in the presence of magnesia ; the quantity of ammonia is expressed in cubic 

 centimeters of tenth-normal acid — let it be n — then the amount of amino acid 

 In 100 cc. of the extract expressed in terms of nitrogen is found by formula : 



^^ '- •. The results obtained are correct within 3 per cent, except in 



the case of tyrosin and histidin, where the error may amount to 10 per cent." 



With this procedure cabbage leaves were found to contain 0.886 per cent of 

 amino acids (expressed as nitrogen per 100 gm. of dry substance) ; tobacco 

 flowers, 0.272 ; turnip leaves, 0.507 ; alfalfa, 0.35 ; and carrot tops, 0.28 per cent. 



About the progress made in the chemistry of food and condiments dur- 

 ing the year 1911, H. Kuttenkeulek (Chem. Ztg., 36 (1912), Nos. 61, pp. 565- 

 568; 63, pp. 585, 586). — This deals with the progress made in food and condiment 

 chemistry, but does not include milk and dairy products, water, brewery prod- 

 ucts, and bacteriology, for which special reports will be rendered. 



Swiss food book (Manuel suisse des Denrdes Aliment aires. Bern, 1910, 2. ed., 

 rev. and enl., pp. XVI +344)- — This describes the oflicial methods of analyses 

 of foods, condiments, waters, beverages, air, etc., of Switzerland. A description 

 of the substances is given in almost every case. 



A new method for determining sugar in potatoes, O. Claassen (Chcm. 

 Ztg., 36 (1912), Nos. 79, pp. I^I-IU; 81, pp. 771, 772.)— This is a study of 

 methods, the results of which indicate that it is not advisable to determine the 

 sugar content of potatoes with the press juice. When press juices are stored for 

 a time, all the saccharose present becomes inverted. When the polarimetric 

 method is used, the influence which the copper-reducing but optically inactive 

 bodies exert is eliminated as a factor. The method is also advantageous from 

 the point of rapidity of execution. 



The use of the hot alcoholic digestion for extracting the sugar was found to 

 be the most feasible procedure. It was also determined that the precipitation 

 of dextrose by lead salts is a process which proceeds very irregularly. 



For the determination of sugar in potatoes, the author advises the use of the 

 polarimetric method for the inverted substance (Herzfeld's method was ad- 

 justed for use with potatoes), and the application of the dextrose formula. 

 From this another formula was derived which can be used where dextrose and 

 saccharose are present at the same time. 



In addition to the above the influence of temperature on the rotation and the 

 space displaced by the potato substance are discussed. 



About the coloration of certain reagents by raw cow's milk in the presence 

 of hydrogen peroxid, EL Nicolas {Abs. in Chem. Ztg., 36 {1912), No. 101, 



