214 



SCIENCE. 



[N. S. Vol. XVI. No. 397. 



T]i€ Determination of Starch in Baking 

 Powders: W. M. Allen. 



Arsenic Pentachloride : Chas. Baskerville 



and H. H. Bennett. 



Penta-halogen compounds of arsenic in 

 which one or more chlorine atoms have 

 been replaced by organic radicals are well 

 known. Sloan {Chemical News, 46, 194) 

 prepared Asl^ and Marignac obtained 

 ASF5. Many workers have failed to pre- 

 pare AsClg — although Sloan {Chemical 

 News, 42, 180) produced a body answering 

 to the formula AsjClg stable at 15° C, hav- 

 ing saturated the trichloride with chlorine 

 at —23°. The authors prepared AsCl^ by 

 following out the same procedure at the 

 temperature of solid carbon dioxide. The 

 greenish-yellow liquid was stable up to 

 —28° C. ; readily lost chlorine with eleva- 

 tion of temperature; dissolved in carbon 

 disulphide and absolute ether cooled to 

 — 30°, crystallizing from the latter on low- 

 ering the temperature a few degrees. 



Preparation of Pure Prwseodymiu^n Com- 

 pounds: Chas. Baskerville and J. W. 

 Turrentine. 



The beautiful but tedious and time-con- 

 suming method of Carl Auer, who split 

 didymium into neo- and pr«seodymii;m, 

 has been followed with alterations in detail 

 by the subsequent workers, viz., von 

 Scheele, Brauner, Dennis and most recent- 

 ly H. C. Jones. The method depends upon 

 prolonged- fractional crystallization of a 

 water solution of the double prseseodymiiun 

 ammonium nitrate acidified with nitric 

 acid. This paper gives an account of a 

 partial repetition of that process, some un- 

 successful efforts to improve upon it, and 

 finally a method giving very satisfactory 

 results. 



Experiments seeking the separation by 

 fusion with sodium peroxide, potassium 

 disulphate ; precipitation by potassiiun 

 chromate (Muthman) and iodate (Gibbs) 



and formaldehyde, gave negative results or 

 observations were made not sufficiently en- 

 couraging to warrant further pursuit. 



The final method depended upon satura- 

 ting a cold concentrated citric acid solution 

 with fairly pure praBseodymium hydroxide, 

 free from ammonia and excess of water. 

 This solution when filtered and heated 

 precipitated a beautiful green citrate, 

 which is insoluble in boiling water, 

 being rapidly washed by the same in a hot 

 funnel until free from acid. Neodymium 

 and lanthanum citrates do not act this way. 

 The purity of the body was determined 

 with a large Rowland grating by Dr. W. 

 J. Humphreys, who made the examinations 

 of the materials iised by Jones. 



The Sidphur Contents of Some Vegetable 

 Materials: W. A. Withers and G. S. 

 Fraps. 



As the average of a number of analyses, 

 we find the ash of plants to contain only 

 a portion of the total sulphur, as follows: 

 cottonseed meal, one-sixth; cottonseed hulls, 

 one-fifth ; oats, one-tenth ; cowpeas, one- 

 sixth; corn, one- fortieth ; peanvits, one- 

 third; tobacco, four-fifths. Plants contain 

 much more sulphur than has generally been 

 considered to be the case. Corn and oats 

 contain more sulphur (as SO3) than pot- 

 ash, soda, lime or magnesia. It is probable 

 that sulphur plays a greater role in plant 

 nutrition than has been suspected. 



Methods of Determining Sidphur in Plants: 



G. S. FRAPS. 



The paper is an account of a study of 

 several methods. Evaporation Avith nitric 

 acid and subsequent ignition with the ad- 

 dition of calcium acetate seems to be the 

 best method. 



Determination of Sulphuric Acid in Soils: 

 C. B. WujLIams (See Jour. Am. Chem. 

 Soc, Vol. XXIV., p. 658-661). 



