1644
JOURNAL O F CHEMICAL EDUCATION
Auousr, 1931
so that the excess solution drawn into the buret will be siphoned back into the bottle and thus give a zero reading on the buret. Occasional readjustment may be necessary, hut it is easily accomplished. The use of the constant level type of buret has proved time saving and satisfactory in this laboratory. ED. F. DEGERING PURDUEU N ~ V E R S ~ T Y LAFAYETTE, I NDIANA
Chemists Deal with Merest Traces in Analyzing Soils. Department chemists find that some problems of soil analysis challenge the accuracy of the most painstaking of scientific workers. Many constituents of agricultural soils occur in such minute quantities, say the soil chemists, t h a t in ordinary analytical work they would be disposed of hy saying there was a "trace." The soil chemist learns to deal in traces. W. 0.Robinson, of soil investigations, Bureau of Chemistry and Soils, illustrates this fact in a discussion of the methods now fallowed in the bureau. "The phosphoric acid determination," bc says, " is a stumbling block to the average analvst. A concrete idea of the importance of accuracy in soil analysis may be had by calculating the increase of phosphoric acid and lime in the soil, as the result of adding a liberal dressing of these fertilizers. An application of 200 pounds of phosphoric acid to the acre will raise the percentage of phosphoric acid in the surface soil by only about one-one-hundredth of 1 per cent." The upper G inches of a n acre of soil weighs approximately 1,750,000 pounds, the chemists have discovered. I n one of the notable achievements of soil science it was found that certain previously unproductive soils in Florida would grow excellent crops of tomatoes if fertilized with only a few pounds per acre of manganese compounds. I n certain tobacco soils the addition of a few pounds of magnesium per acre has made differcnces in production that have fairly astounded the growers. I n dealing with such infinitesimal traces of chemical substances, chemists are forced to use the purest reagents available, and to give the most scrupulous attention to their methods. In some proccsscs it is necessary to use only platinum vrsse1s.-The Oficiel Record of the Lf. S. Depl. Agrirullzrre Marine Animals Analyzed to Learn Life Needs. Zoijlogists studying the life of the sea are now calling chemists in to their aid. Dr. Paul S. GaltsoK of the U. S. Bureau of Fisheries told the American Association for the Advancemcnt of Science a t its recent meeting in Pasadena. Such studies have become necessary because of discoveries of the great fluctuations, even from day to day, in the concentration of necessary chemical elements in sea water, and also because of the new knowledge of the great importance of some elements, like copper and manganese, present in only the minutest amounts. Oysters, for example, were discovered by Dr. Galtsoff to require a trace of copper, but no more than a trace, before they abandon the wandering habits of their youth and settle down on the bottom to grow f a t and profitable far oystermen. There is practically no copper in pure sea water but there is a little in river water, so that oyster beds are almost invariably found near the mouths of rivers. Another example of the importance of a cbemical-biological understanding of the life of the sea cited by Dr. GaltsoK was the work of sea animals, particularly the miuoscopic forms, in depositing lime beds that eventually became limestone. The annual deposit of limy material laid down by living animals in the sea amounts to 1,400,000,000 tans.-Science Seruice
