377 



in its foul state had given very obvious indications of both sulphur 

 and ammonia; but neither of these substances could be detected 

 after its spontaneous depuration. 



The source of these new saline bodies is referrible to the organic 

 substances, chiefly of an animal nature, which are so copiously de- 

 posited in the Thames. The depurating process may be denomi- 

 nated a species of fermentation, in which the softer and more soluble 

 animal compounds act as the ferment, and are themselves destroyed, 

 while the salts that were attached to them are left behind. Hence, 

 the more foul the water the more complete the depuration ; and it 

 is on this principle that the popular opinion of the peculiar fitness of 

 Thames water for being used at sea may be explained ; its extreme 

 impurity inducing a sufficient degree of fermentation to effect the re- 

 moval of all those substances which might induce any future renewal 

 of that process. 



On the Composition of Chloride of Barium. By Edward Turner, 

 M.D. Professor of Chemistry in the University of London. Com- 

 municated by Dr. Dionysius Lardner, F.R.S. Read May 14, 1829. 

 [Phil. Trans. 1829, p. 291.] 



The frequent employment of chloride of barium in delicate chemi- 

 cal investigations, renders an exact knowledge of its composition pe- 

 culiarly desirable ; and this has become a more important object of 

 inquiry since it has been made by Dr. Thomson the basis of his calcu- 

 lations of the chemical equivalents of sulphuric acid, and of thirteen 

 metals and their protoxides. He has deduced from his experiments 

 with the chloride of barium the number 36 as the equivalent of 

 chlorine ; 70 as that of barium ; and 78 as that of baryta ; whence 

 the equivalent of the chloride of barium would be 106 ; and accord- 

 ingly, on mixing this quantity of the chloride with 88 parts of sul- 

 phate of potash, each being previously dissolved in separate portions 

 of distilled water, he finds a complete double decomposition has taken 

 place ; the resulting sulphate of baryta, reduced to dryness, weigh- 

 ing 118 parts, and the muriate of potash yielding 76 parts of chlo- 

 ride of potassium. Hence he infers that 40 is the equivalent number 

 for sulphuric acid, and 48 that for potash. Berzelius, however, 

 maintained that this experiment, as well as the deductions from it, 

 are not exact. Dr. Thomson having, in consequence of Berzelius's 

 objections, repeated his experiments, still asserts their accuracy. The 

 author of the present paper investigated the subject with the greatest 

 care, employing materials in a state of perfect purity, and obtained 

 results which coincided with those of Berzelius. He details the pre- 

 cautions he took for ensuring the conditions of perfect purity in the 

 substances with which his experiments were made, and to the neglect 

 of which he traces some of the errors which he imputes to Dr. 

 Thomson's analysis. But there exists also a more radical cause of 

 error in the method employed by that chemist ; for Dr. Turner finds 

 that when solutions of muriate of baryta and of sulphate of potash 



