Chemistry and Physics. 539 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Quantitative Separation of Beryllium and Aluminium. 

 — It is well understood that the methods in use for making the 

 separation under consideration are somewhat inconvenient or 

 unsatisfactory, so that a more simple method, and one which 

 appears to give very accurate results, is worthy of attention. B. 

 Glassmann carries out the analysis as follows: The hydrochloric 

 or sulphuric acid solution of the metals is nearly neutralized with 

 sodium carbonate, an excess of sodium thiosulphate solution is 

 added, and the liquid is boiled until the odor of sulphur dioxide 

 has disappeared. Then the liquid is heated on the water bath 

 for half an hour. The precipitate, consisting of aluminium 

 hydroxide mixed with sulphur, is washed and ignited. After the 

 excess of thiosulphate in the filtrate has been decomposed with 

 hydrochloric acid, the beryllium is precipitated as hydroxide, 

 either with ammonia, or, as the author prefers, with a mixture of 

 potassium iodide and iodate. In order to use the latter method 

 sodium hydroxide solution is added to the liquid until a precipi- 

 tate begins to form, and then the precipitate is dissolved in a few 

 drops of dilute acid. Then an excess of a mixture of equal vol- 

 umes of about 25 per cent potassium iodide solution and satu- 

 rated potassium iodate solution is added. After about five 

 minutes the separated iodine is decolorized by the addition of 

 exactly the proper amount of 20 per cent sodium thiosulphate 

 solution, and then a small amount of the iodide and iodate mix- 

 ture is added in order to make sure, by the fact that it does not 

 produce an instantaneous separation of iodine, that enough has 

 been added. Then a few drops of sodium thiosulphate are 

 added, and the liquid is heated on the water bath for half an 

 hour. The precipitate is easily filtered, on which account the 

 method is recommended, and also because the liquid, being abso- 

 lutely neutral, does not act as much upon glass as do alkaline 

 solutions. — Berichte, xxxix, 3366, 3368. h. l. w. 



2. The Temperature- at which Water Freezes in Sealed Tubes. 

 — Miees and Isaac have shown that in cooling a supersaturated 

 solution in which a few crystals are growing while it is being 

 stirred, the refractive index rises until at a certain temperature it 

 attains a maximum value and then suddenly falls ; at this moment 

 also profuse crystallization takes place. They concluded that this 

 is the temperature of spontaneous crystallization. These investi- 

 gators have now made numerous experiments with water con- 

 tained in sealed tubes which were violently and continuously 

 shaken by hand, while being very slowly cooled in a bath of 

 brine, until rapid crystallization of ice took place. Various 



