496 SoimUfic Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Separation of Lithium from Potassium a ml Sodium. — 

 Samukl Palkin has modified the old method of Rammelsberg, 

 which consisted in treating the dry chlorides with a mixture of 

 anhydrous alcohol and ether in order to dissolve the lithium 

 chloride. This method is known to be unsatisfactory, both on 

 account of the tendency of lithium chloride to be partially con- 

 verted into the insoluble carbonate when dried in the air, and 

 also on account of the occlusion of some of the lithium chloride 

 by the insoluble chlorides of sodium and potassium. The present 

 method avoids these difficulties by precipitating the greater part 

 of the sodium and potassium chlorides in the first place by add- 

 ing alcohol slowly and then ether to a slightly acid, very concen- 

 trated aqueous solution of the chlorides, then after filtration on a 

 Gooch crucible, evaporating the filtrate to dryness, taking up the 

 residue with absolute alcohol containing a drop of hydrochloric 

 acid, adding ether until the small amounts of sodium and potas- 

 sium chlorides are completely precipitated, and collecting the 

 precipitate with the original one. One volume of alcohol to 

 about 5 volumes of ether is the mixture recommended for the 

 precipitations and for washing. From the results of test analyses 

 it appears that the method gives excellent results. However, it 

 does not seem probable that the method will supersede in general 

 analytical practice the more convenient and very satisfactory 

 method of Gooch, unless, perhaps, there may be some who pre- 

 fer the fumes of ether to those of amyl alcohol. — Jour. Amer. 

 Chem. Soc, xxxviii, 2326. h. l. av. 



2. The Action of Light upon Iodine and Iodide of Starch. — 

 It is stated by M. H. Bordier that not only does the well-known 

 blue iodide of starch form colloidal solutions, but that the solu- 

 tion of iodine itself in water is also colloidal, showing ultra- 

 microscopic particles. He has found that sunlight has an action 

 upon very dilute solutions of these two substances. For instance, 

 when 10 drops of 10 per cent tincture of iodine are added to 

 1000 cc of water with agitation after the fall of each drop, a pale 

 yellow solution containing about 18 mg of iodine is obtained. If 

 a little starch paste is then added a blue color is obtained and 

 this disappears after several hours of exposure to sunlight. More- 

 over if the iodine solution is exposed to sunlight first and the 

 starch paste is added afterwards, no blue color is produced. The 

 author's explanation is that the iodine simply goes into the ionic 

 condition under the influence of the light, but this does not 

 appear to be a very satisfactory explanation. The reaction was 

 applied to a test of the colored glasses used for bottles to protect 

 substances from the action of light, and it was found that the 

 yellow glass most extensively employed for this purpose gives no 



