Chemistry and Physics. 87 



duced metal being protected from contact with the crucible. On 

 treating the mass with water small hexagonal crystals of beryl- 

 lium were obtained mixed with pulverulent metal and oxide. To 

 determine whether beryllium oxide could act as an acid oxide and 

 form beryllates the freshly precipitated hydroxide was digested 

 in alcoholic solution of potassium hydroxide until it was sat- 

 urated, care being taken to exclude carbon dioxide. On evapo- 

 ration over sulphuric acid, a white silky mass was obtained which 

 gave a formula closely approximating Be(OK) 2 . To determine 

 the basicity of beryllium oxide, absolute alcohol was saturated 

 with sulphur dioxide gas, and pure, recently precipitated beryl- 

 lium hydroxide was dissolved in it to saturation. On evaporation 

 over sulphuric acid, a white crystalline residue consisting of 

 minute hexagonal plates was obtained which on analysis corres- 

 ponded to the formula BeS0 3 . With boric acid, a borate 

 Be.B 2 8 was obtained. — Ber. Berl. Chem. Ges., xxiii, 727, Mch. 

 1890. G. F. B. 



2. On the estimation of the Molecular mass of Colloids by the 

 method of Raoidt. — Sabaneeff has made a series of experiments 

 to determine the molecular mass of certain colloid substances by 

 means of the freezing points of their aqueous solutions. Col- 

 loidal tungstic acid, for example, dried at 200° and containing 

 2*57 per cent of water, corresponding to the formula H 2 W 3 O 10 

 which requires 2*52 per cent, has a molecular mass calculated 

 from the observed lowering of the freezing point, varying be- 

 tween 677 and 995 ; while that represented by the formula 

 H 2 W 3 O 10 is 7 J 4. Colloidal molybdic acid forms minute hygro- 

 scopic plates, which dried over sulphuric acid for several weeks 

 still contain 6*99 per cent of water. It dissolves with difficulty 

 in water and produces a lowering of the freezing point corres- 

 ponding to a molecular mass of 620; that required by (Mo0 3 ) 4 

 being 576 and that corresponding to tetra-molybdic acid H 2 Mo 4 13 

 being 594. For glycogen the molecular mass found was as a 

 mean 1585, corresponding to the empirical formula increased ten- 

 fold (C 6 H 10 OJ 10 , which requires 1620. Dried at 115°, however, 

 this substance possesses a molecular mass one and a half times 

 less. The lowering of the freezing point produced by colloidal 

 silicic acid was so slight that the values obtained all came within 

 the limits of observational errors. Colloidal iron hydroxide 

 could not be obtained free from chlorine ; the purest solution con- 

 taining one molecule of FeCl 3 to 116 molecules Fe(OH) 3 . On 

 the assumption that the molecular mass of the hydroxide is so 

 great that its influence in producing the slight depression of the 

 freezing point observed may be neglected, the author calculates 

 from the observed data a molecular mass of 300 corresponding 

 to the formula Fe 2 Cl 6 which requires 325. — J. Buss. Phys. Chem. 



Ges., 1889,515; Ber. Berl. Chem. Ges., xxiii, (Ref.) 87, Mch. 



1890. G. F. B. 



3. On the Color of Fluorine and on its Spectrum. — Moissaist has 

 examined the color of fluorine as seen through a platinum tube 



