486 DR JOHN MURRAY AND MR ROBERT IRVINE ON THE 



not to solution of calcareous organisms. So that the sulphur (S) — of the sulphuric acid 

 (S0 3 ) present as sulphate of lime in sea-water — is abstracted and fixed, in a mud deposit 

 containing iron, as sulphide of iron (FeS),* while the carbonic acid takes the place of 

 the sulphuric acid, and an amount of carbonate of lime (CaC0 3 ) is formed in proportion 

 to the sulphur thus removed. The presence of iron is not, of course, necessary for the 

 reaction, and there may be carbonates formed other than carbonate of lime, as this 

 reaction applies as well to the sulphur salts of magnesia and the alkalies. The figures in 

 Tables II. and IV. show that the waters there referred to exhibit the changes here 

 indicated, but we seldom find the gain of alkalinity (or carbonate) exactly equivalent to 

 the decrease of sulphuric acid. For instance, in Table III., 4th portion, the decrease of 

 sulphuric acid would only account for 0*432 gramme excess of carbonate of lime instead 

 of 0*6057, which was found ; in Table VII. only 0*1205 gramme excess would be accounted 

 for instead of the 0*2281 Gramme found. 



O 



The increase of alkaline ammoniacal salts points, however, to a further reaction, by 

 which carbonate of lime is increased in a slight degree, for as ammonium carbonate 

 [(NH 4 ) 2 C0 3 ] is formed by the decomposition of the albuminoids present, the sulphates in 

 the sea- water by this means are decomposed, sulphate of ammonia [(NH 4 ) 2 S0 4 ] and 

 earthy carbonates being the result. This, while not accounting for the total increase of 

 alkalinity in the mud-waters, accounts for some of the deficiency noted above, as we shall 

 see presently. 



Table IV. shows the decrease of sulphur, as sulphuric acid, and the consequent 

 increase of alkalinity, calculated as carbonate of lime, to be very marked. The decrease 

 of the former will be seen to range from 0*9757 to 1*0849, while the increase of the 

 latter ranges from 1*0145 to 1*3566. Indeed, the waters referred to in Tables II. and 

 IV. may be taken as typical, and show the changes from the normal effected in the sea- 

 water associated with marine muds. 



The following table (A.) has been constructed to show that these two reactions, viz., 

 the deoxidation of sulphates by organic matter, and the decomposition of albuminoids 

 into ammonia, are sufficient to produce the high alkalinity observed in the waters in 

 Tables II. and IV. 



Column a shows the decrease of sulphuric acid from that present in normal sea- water. 



Column b shows the calculated equivalent, as carbonate of lime, of the decrease of 

 sulphuric acid in column a, 



Column c shows the calculated equivalent, as carbonate of lime, of the ammonia found 

 by analysis in the mud-water. 



As any precipitation of carbonate of lime out of the mud- water necessarily takes away 

 from the resulting alkalinity, column d gives the difference between the total lime found 

 in normal sea- water (calculated into carbonate of lime) and that in mud-water. 



By adding the figures in column b and c, we get the increase of alkalinity due to the 

 deoxidation of sulphates and to the presence of ammonia ; and subtracting the figures in 



* Reaction shown on page 496. 



