12 EXPERIMENT STATION RECORD. [Vol.41 



with considerable accuracy the H-ion concentration of small quantities of 

 solution. The indicators described are blue and red lacmoid papers, methyl 

 orange paper with a range of pH of from 2.4 to 3.8, bromophenol (pH 3.4 to 

 4.6), alizarin sodium sulphonate (pH 4 to 6), neutral red (pH 7 to 9), and 

 azolitmin (pH 6.2 to 8). It is considered advisable when dealing with very 

 small volumes of solution to check the indicator paper determinations by the 

 supplementary use of the spot plate method, in which the H-ion concentration 

 Is determined in a drop or two of the solution by comparison of the color pro- 

 duced by a certain indicator in the same quantity of buffer solution of known 

 pH value. 



With the described methods, it is considered possible to obtain a pH value 

 differing 0.4 to 0.02 pH or even less from those obtained by the more exact 

 methods. 



The determination of iodid in mineral waters and brines, W. F. Baughman 

 and W. W. Skinnek {Jour. Indus, and Engin. Chem., 11 (1919), No. 6, pp. 563- 

 568). — The authors at the Bureau of Chemistry, U. S. Department of Agricul- 

 ture, report an investigation of various methods for the determination of 

 iodin in the presence of chlorid and bromid as a result of which the perman- 

 ganate method is recommended as the most satisfactory, provided certain 

 directions which are given in detail are observed. In regard to other methods 

 the following conclusions are drawn : 



" Distillation with potassium bichromate will not completely liberate iodin 

 from iodids. Iodid in the presence of as much as 10 gm. sodium chlorid can 

 be determined with satisfactory results by distilling with ferric sulphate. 



" Iodid can be determined quite accurately in the presence of bromid by a 

 single distillation with ferric sulphate if the quantity of bromid present in the 

 sample does not greatly exceed 0.4 gm. This method is especially recommended 

 for removing iodin from the sample which is to be used for the bromid deter- 

 mination. 



" Iodin may be determined in the presence of large amounts of bromid by 

 making a double distillation with ferric sulphate. However, this method is 

 more tedious and time-consuming than the permanganate method, and the 

 results obtained not quite so accurate." 



Studies on the behavior of inulin in the animal body. — Application of the 

 Benedict method to the estimation of levulose and inulin, R. Okey (Jour. 

 Biol. Chem., 38 (1919), No. 1, pp. 33-42). — The author reports a series of tests 

 on the application to the estimation of levulose and inulin of the modification 

 of the Levris-Benedict method for sugar determination developed by Benedict 

 and Osterberg (E. S. R., 39, p. 112). The method was found satisfactory for 

 the determination of levulose and of levulose in the presence of inuUn. 

 Attempts to determine Inulin quantitatively by hydrolysis with the picrate- 

 picric acid and colorimetric determination of the levulose in the same solution 

 proved unsuccessful, owing to the formation of products which on heating, 

 after the addition of the carbonate, gave colors increasing in depth with the 

 time of heating in the acid solution and becoming more intense than those 

 from equivalent quantities of levulose. An increase in depth of color was 

 also produced when glucose and levulose solutions were heated with the acid 

 picrate before the addition of the carbonate. 



Hydrolysis of the levulin with hydrochloric acid led to a retardation of the 

 rate of color development which was proved to be due to the salts formed 

 by the neutralization of the acid. It was found that this interference may be 

 avoided by increasing the time of heating with the carbonate to 15 minutes, 

 or by using the higher concentration of the picrate-picric acid recommended 



