171 ^ 



XVIII. 



THE CHEMISTRY OF FOUL MUD DEPOSITS. 



By E. A. LETTS, D.Sc, &c., and FLORENCE W. REA, B.Sc. 



[communicated by dr. w. e. adeney.] 



[Read November 28, 1916. Published January 4, 1917.] 



This question does not appear to have received the attention which in view 

 of its importance it would seem to deserve. 



It divides itself naturally into two parts, viz. : — 



1. More or less theoretical, as to the mechanism of the reactions leading 



to the evolution of sulphuretted hydrogen, and 



2. The actual chemical changes occurring in foul mud deposits. 



As regards the first of these two questions it is known that the evolution 

 of the gas may be due to one or other. of two causes, viz., first, the decom- 

 position of albumenoid bodies, and the second, the decomposition of sulphides 

 by acids, the sulphides being probably formed by the reduction of sulphates 

 originally present ; the acids being formed in all probability as products of 

 the decomposition of the organic matter originally present. 



Dittmar, in the " Challenger Reports," 1 states that the sulphates present 

 in sea-water are those of potassium, magnesium, and calcium. 



Now, the question arises, which of the two above-named causes is usually 

 active in the evolution of the gas, and, if both, what is the extent of each ? 



One of the authors of this paper, some years ago, suggested to Mr. J. L. 

 M'Kee, b.a. (at that time one -of his pupils in the Queen's University of 

 Belfast), that he should submit this matter to an experimental investigation, 

 and the results of his experiments will be found in Appendix VI to the 

 seventh report of the Royal Commission on Sewage Disposal. 2 



1 Challenger Report, in which Dittar gives the amounts of the sulphates present in 

 sea-water as being approximately 100 per parts of the dried solids : potassium sulphate, 

 2 - 465 ; magnesium sulphate, 4-323 ; and calcium ditto, 4'070. 



3 " The Pollution of Estuaries and Tidal Waters," by Professor Letts and Dr. W. E. 

 Adeney. 



SOLENT. PROC. B.D.S., VOL. XV., NO. XVIII. 2 P 



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