488 



DR JOHN MURRAY AND MR ROBERT IRVINE ON THE 



In the water filtered from various saiidy muds, exposed to the scouring action of tides, 

 little chemical change was noticeable, and we did not find any notable difference between 

 the composition of the water associated with them and normal sea-water, unless it were 

 a slight increase in the alkalinity. 



Composition of Sea- Water Salts in Mud- Waters. — At the outset of this paper, it was 



stated that the result of Forchhammer's and Dittmar's numerous analyses of sea- water 



was to show that the composition of the sea-salts is practically constant. Hence it 



follows that the quantity of chlorine in an ocean water, at a given temperature, is 



proportional to the excess of its specific gravity over that of pure water at the same 



St— W« 

 temperature. This is expressed by the formula - — 77 — = D, where 4 S t denotes the specific 



gravity of sea-water and 4 W t that of pure water, both referred to pure water at 

 + 4° C = 1000. x represents the chlorine, and D a constant. 



Dittmar found the D constant in ocean water to be almost uniformly 1*4606 at zero 

 temperature.""" As an example, taking water of density 4 S 15 . 5G 1026, which is equal at 

 S to 1028'31, and the chlorine value of which is 19'382, we have 



S -1000 ^ . n 102831-1000 , . OAA 

 —5 = D ovva. figures , n . nnn = T4600. 



X 



19-382 



In the mud-water of Table IV., the D values, when calculated as above, are as 

 follows : — 



1st portion, 



1-4600 



2nd „ 



1-4390 



3rd „ 



1-4340 



4th „ 



1-4340 



5th „ 



1-4320 



6th „ 



1-4230 



It will be observed that these values are by no means constant, and are all below the 

 normal value, thus clearly indicating a change in the composition of the sea- water salts. 



In looking at Table IV., where all the data are for convenience reduced to density 

 1026, — which may be taken as the average specific gravity of sea- water, — the halogen 

 (chlorine found) in the first column is seen to increase regularly in the several portions 

 above what is found in normal sea- water of density 1026, the difference ranging from 

 0"009 to 0509 gramme. In another column of the same table, the total bases (as sul- 

 phates) are also seen to increase from 0*334 to 0703 gramme. Here, therefore, we cannot 

 take, as is usual, the density, the chlorine, nor the total bases (as sulphates) as standards 

 to calculate from, so as to arrive at the true chemical composition of the sea- water salts, 

 for not one of these three is constant in amount, nor bears any definite relation to the 

 other components. It follows from this that any mixture of such a mud- water with 

 ordinary sea-water would entirely alter the relation generally found to exist between the 



* Sec Dittmar, op. cit., part i. p. 56. 



