460 Chronicles of Science. [July, 



found to be phosphate of alumina, formed in consequence of the slight 

 solubility of alumina in ammonia, and in sulphide of ammonium. 



Lastly, the same author read a note showing that in minute and 

 exact analyses the mineral constituents of filter paper must be taken 

 into account. A careful analysis of the ash of such paper has shown 

 it to consist chiefly of clay and carbonates of lime and magnesia, 

 with ferric oxide ; but besides these, sulphates of potash, soda and 

 lime, with traces of phosphoric acid and oxides of cobalt and lead, 

 were present. 



In an interesting communication " On the Periodides of some Or- 

 ganic Bases," Mr. Tilden made known the existence of several new 

 compounds having a constitution like that of the iodo-sulphate of 

 quinine, and possessed of similar optical properties. For a full 

 account of these bodies we must refer the reader to the ' Journal of 

 the Chemical Society ' for April. 



A paper, read by Dr. J. H. Gladstone, " On the Specific Refractive 

 Energies of the Elements and their Compounds," belongs to Physics 

 rather than Cbemistry, and will be noticed in another place. 



The last paper we can notice was by Dr. Miller, " On some Points 

 in the Analysis of Potable Waters." The greater part of this valuable 

 paper was devoted to an account of the method pursued by the author 

 in the determination of organic matters. It is well known that the 

 greatest discrepancies sometime occur in the statements of different 

 chemists regarding the same water, and Dr. Miller described the precau- 

 tions necessary to ensure exact results by the incineration process. He 

 also described at some length the mode of determining the amount of 

 cxidizable organic matter by means of a standard solution of perman- 

 ganate of potash. This reagent, although it does not discriminate be- 

 tween different kinds of organic matter, still affords tolerably precise 

 indications of the quantity present, and moreover is most readily acted 

 on by those matters which are most objectionable in water. In reply 

 to the objection that the presence of nitrites might affect the test, Dr. 

 Miller said that it was easy to discriminate between these and actual 

 organic matters, since the former decolorized the solution instantly, 

 and the action of the latter was progressive ; so that the pink solution 

 might be added until the water became permanently coloured, and the 

 subsequent slow decolorization might be set down to organic matters. 

 As a positive test for the presence of nitrites, the author gave that 

 proposed by Dr. Price, viz. a solution of icdine of potassium and starch 

 with a drop of dilute sulphuric acid, but we may : tate that this test is 

 open to a fallacy, since iodine is , et free when chlorides and nitrates 

 are present, and nitrites altogether absent. For the determination of 

 nitrates, Dr. Miller recommended the process of Dr. Pugh, which is 

 no doubt well known to our readers. In the discussion which fol- 

 lowed, the advisability of adopting a uniform method of stating the re- 

 sults of an analysis was strongly dwelt upon by several chemists, and 

 it is to be hoped that the publication of this valuable paper will con- 

 tribute to that end. It was announced for publication in a forth com- 

 ing number of the ' Journal of the Chemical Society,' and we shall 

 probably have occasion to refer to it again. 



