280 CARNEGIE INSTITUTION OF WASHINGTON. 



worked at the laboratory upon the physicochemical properties of the 

 constituents of cereals, especially glutenin and gliadin, the components 

 of wheat gluten, under the direction of Professor Lawrence J. Hender- 

 son. This work included not only scientific study, but also practical 

 application of the results to the process of bread-making and the more 

 efifective utilization of wheat substitutes. The physicochemical appa- 

 ratus and books belonging to the Carnegie Institution of Washington 

 at the laboratory were put at the service of these investigators and 

 enabled them to carry out researches which would otherwise have been 

 impossible and which are leading to highly important results. 



Owing to the departure into Government service of most of the other 

 assistants at the laboratory, a smaller amount of work was possible 

 than would otherwise have been accomplished; but several results of 

 interest and significance were nevertheless secured, as follows: 



1. Refractive Indices of the Nitrates of Lead Isotopes. 



With the assistance of Dr. Walter C. Schumb, the refractive index of 

 the nitrate of pure common lead was compared very carefully with that 

 of the nitrate of uranio-lead prepared from the Australian material 

 mentioned in previous reports. The two samples of nitrates were sep- 

 arately recrystallized with care, and finely developed crystals were 

 measured in the Abbe-Zeiss total-reflecting crystal refractometer. A 

 solution of sulphur in methylene iodide having a refractive index of 

 1.79 was used as the contact liquid and very careful measurements 

 were made of many crystals in varying positions. The refractometer 

 was standardized by means of a polished glass prism possessing an 

 exactly known refractive index which could be verified by the method 

 of minimum deviation. The refractive index of common lead nitrate 

 at 20° was found to be 1.7815 and that of uranio-lead nitrate was found 

 to be 1.7814, each value being a mean of many concordant determina- 

 tions. Thus the difference in atomic weight shown by the two speci- 

 mens of lead (the atomic weights are respectively 207.20 and 206.41) 

 has no appreciable effect on the refractive index of the salt — a highly 

 interesting and newly discovered fact. 



2. Solubilities of the Nitrates of Lead Isotopes. 



Dr. Schumb assisted also in the following work : The two specimens 

 of lead nitrate which had been purified (crystals of which had been used 

 in the preceding investigation) were investigated with great care as to 

 solubility, using a method described on page 301, Year Book No. 16, 

 with small but convenient improvements. Greater difficulty was 

 found in obtaining an exactly saturated solution than was the case 

 with sodium sulphate, at least 24 hours at perfectly constant tempera- 

 ture being needed in order to obtain constant results. The weighed 

 portions of solution, saturated at 25.02°, were evaporated with excess 

 of sulphuric acid and the sulphate was gently heated at 350° until con- 

 stant in weight. Four such determinations with ordinary lead nitrate 



