8 EXPERIMENT STATION RECORD. 



■vegetable i;roteids are bygroscopie', so it is almost impossible to use anbydrous 

 material for analytical purposes. Accurate determinations of tbe water content 

 are tberefore essential in reporting analyses. 



" Tbe usual custom of investigators bas been to determine tbe moisture by 

 beating in an air batb at 110° C, and as tbe results in tbis paper sbow, the 

 determinations tbus made may readily be subject to an error of 1 per cent. 

 Obviously an error of 1 per cent or more in the water determinations would 

 result in an error of one-balf of 1 per cent in tbe carbon determinations, and a 

 measurable error in tbe determination of nitrogen. It can only be said that in 

 the majority of researches on tbe animal or vegetable proteins, the carbon and 

 nitrogen determinations are in large measure only used for comparative observa- 

 tions, and hence the absolute nitrogen or carbon content is not of as great 

 importance. It is clear, however, that at least so far as tbe materials used 

 in these investigations are concerned, it is impossible to' determine tbe moisture 

 content in them by drying in hot air at a temperature of 100 to 110°. 



" The removal of the final traces of moisture which are persistently retained 

 bj' tbe proteins when dried in an air bath at a temperature of 110° can be 

 effected by subsequent desiccation in a high vacuiun for 2 weeks." 



The detection and estimation of reducing sugars, S. R. Benedict {Jour. 

 Biol. Cheiii., 3 (1907), Xo. 2, pi). 101-117). — From a study of methods of esti- 

 mating sugar, the author recommends a copper-carbonate solution and gives 

 directions for its preparation. For delicate work in sugar detection, either in 

 pure solutions or in urine, the reagent should be freshly mixed and diluted. 



The method outlined for the volumetric estimation of sugar requires a solu- 

 tion of crystallized copper sulphate in water, a solution of crystallized Rocbelle 

 salt with pure anbydrous sodium carbonate, and a solution of potassium sul- 

 lihocyanid. " For use these solutions are mixed in equal proportions in the 

 order indicated. To every 30 cc. of the solution thus obtained are added from 

 2.5 to 5 gm. of pure anhydrous sodium carbonate. The amount of tbis substance 

 added should roughly correspond to the dilution to which tbe solution will be 

 subjected during tbe titration, i. e., for titrating dilute sugar solutions add 

 greater quantity of carbonate and vice versa. The solutions ai'e mixed in a 

 beaker of suitable capacity, the requisite quantity of carbonate added, and the 

 mixture heated to boiling over a gauze until tbe carbonate completely dissolves. 

 Thirty cc. of this mixture (equivalent to 10 cc. copper sulphate solution) are 

 equal to approximately 0.073 gm. of pure dextrose. 



" The titration is carried out as follows : The sugar solution is run in from a 

 burette rather rapidly (not so rapidly as to interfere markedly with continuous 

 vigorous boiling) until a heavy, chalk-white precipitate is formed and the color 

 of the fluid begins to lessen perceptibly. Tbe last portions should be run in in 

 quantities of from 2 to 10 drops (depending on depth of color renaaining and 

 the relative strength of tbe sugar solution), with a vigorous boiling of alx)ut 

 one-fourth minute between each addition. Tbe end point of tbe reaction is the 

 complete disappearance of the blue coloi". Tbis point is sharp and satisfactory. 

 The precipitate obtained is chalk-white and is rather an aid than a hindrance 

 to the determination of tbe end point." 



Separating starch, and glycogen, E. Baub and E. Polenske {Arb. K. Gsndht- 

 smnt.. 2.'t {1906). ?\o. 3. pp. 576-5S0 ; abs. in Zentbl. Oesam, Physiol, u. Patli. 

 Stofficech-sels, ii. ser., ,i {1907), Xo. 2, p. 79). — In the examination of sausage a 

 method of separating starch and glycogen is desirable, and that elaborated by 

 the author depends upon the fact that glycogen is soluble in a saturated solution 

 of ammonium suli)hate. while starch is not. After filtration and dilution the 

 glycogen is precipitated with alcohol. Comparative tests showed that the 

 method gave satisfactory results. 



