August 14, 1908] 



SCIENCE 



219 



potassium has been found to lessen the toxie 

 effect of magnesium salts. The leafy portion of 

 the seedlings appeared normal. The toxicity of 

 the magnesium salts was shown by comparing 

 growths in these solutions with those in distilled 

 water. The toxic effect of magnesixim is greater 

 when there is a deiicieney in potassium. Lime 

 added to such solutions is beneficial, but is not 

 believed to be a substitute for potassium. 



Abstracts have not been received for the fol- 

 lowing papers: 



The Spontaneous Oxidation of Cystein and 

 Gystin: Albert P. Mathews. 



Investigations on Wheat Oil: Joseph S. Cham- 

 BEELAiN and Geokge L. Bidwell. 



Phosphorus Metaholism Experiments : F. C. Cook. 



Artificial Digestion with Organic Acids and mth 

 Essential Oils: Edward Gudeman. 



Hydrolyses of Carbohydrates loith Blood Serums: 

 Edwakd Gudeman. 



Composition of Cold-stored Poultry: M. E. Pen- 

 nington. 



On Nucleic Acids: P. A. Levene. 



The Digestibility of Corn Meal: L. H. Meerhi. 



INORGANIC CHEinSTET 



Philip E. Browning, Chairman 

 The Estimation of Potassium in Soils as the 



Cobalti-Nitrite : W. A. Drushel. 



It was first shown by Karl Gilbert, of Tubingen, 

 ten years ago that potassium is quantitatively 

 precipitated by sodium cobalti-nitrite as the 

 double cobalti-nitrite of sodium and potassium, 

 if the mixture is allowed to stand from 10 to 

 20 hours. Two years later Adie and Wood used 

 the same reagent for the quantitative estimation 

 of potassium, decomposing the precipitate by 

 boiling with dilute sodium hydroxide, and titra- 

 ting the nitrites with standard potassium per- 

 manganate. Their method has been shortened by 

 evaporating the mixture nearly to dryness after 

 adding an excess of sodium cobalti-nitrite, in- 

 stead of allowing it to stand 10 to 20 hours, and 

 by oxidizing the precipitate after washing well 

 with a sodium chloride solution, directly with 

 dilute, hot, standard permanganate instead of 

 decomposing the precipitate and removing the 

 cobalt. The oxidation is completed by acidula- 

 ting with dilute H-SO,, the excess of perman- 

 ganate bleached with standard oxalic acid and 

 the solution titrated to color with permanganate. 

 One cubic centimeter of decinormal perman- 



ganate is equivalent to .000857 gram K-O, since 

 the cobalt is reduced from the trivalent to the 

 bivalent condition. For potassium in soils a 

 weighed amount of soil is digested with 20 per 

 cent. HCl; the extract is evaporated to dryness 

 and gently ignited to remove any ammonium 

 chloride and organic matter present. This residue 

 is then extracted with water acidulated with 

 acetic acid. The extract thus obtained is treated 

 with concentrated sodium cobalti-nitrate and the 

 process carried out as previously indicated. 

 Potassium in Animal Fluids as the Cobalti- 

 nitrite: W. A. Dkushel. 



For potassium in urine the dried residue from 

 a measured quantity is treated with a 9 : 1 nitric- 

 sulphuric acid mixture in a covered platinum 

 dish over the steam bath. After the violent oxi- 

 dation is over the cover is removed, and the solu- 

 tion evaporated to dryness. The residue is then 

 ignited, gently at first and finally at the full heat 

 of the bunsen burner. In the case of protein-con- 

 taining fluids, as the blood, lymph, serum and 

 milk, it is preferable to oxidize the dried residue 

 with concentrated nitric acid alone over the 

 steam bath. The solution is then evaporated to 

 dryness, gently ignited, moistened with concen- 

 trated H2SO4, and ignited as in the case of urine. 

 The residue thus obtained contains nothing which 

 might interfere with the cobalti-nitrate method; 

 it is, therefore, dissolved as may be over the 

 steam bath with a little water acidulated with 

 acetic acid, and, without filtering, the solution 

 is treated with an excess of sodium cobalti- 

 nitrite. From this point the process is carried 

 out as described for soils. The cobalti-nitrite 

 method is applicable in the absence of mineral 

 acids and the salts of ammonium, cesium, 

 rubidium and thalliiim. The method is rapid 

 and for small amounts of potassium com- 

 pares favorably with the ehlorplatinate method 

 if proper care be taken in washing and oxidizing 

 the precipitated potassium sodium cobalti-nitrite, 

 the chief sources of error being the slight solu- 

 bility of the precipitate (1 part in 25,000 to 

 30,000 of water) and in its tendency to include 

 traces of sodium cobalti-nitrite. In this work the 

 chlor-platinate method was used as a control. 

 Electrolytic Determination of Nitric Acid: OwEN 

 S. Shinn. 



It was found that by keeping copper in solu- 

 tion, either by the addition of copper sulphate 

 during reduction, or by retarding the speed at 

 which the anode rotates, the nitric acid is com- 

 pletely reduced to ammonia. This may be de- 



