REPORT ON THE COMPOSITION OF OCEAN-WATER. 
77 
I now proceed to give a table (VIII.) for reducing a given specific gravity to chlorine 
(grams per kilogramme) ; i.e., to find x from 4 S ( . In using this table it must be under- 
stood that the values 4 S, are those corresponding to my experimental conditions, and 
not reduced to the vacuum. Hence, if the given specific gravity is corrected for the 
displaced air, begin by adding 0*033. Supposing the value 4 S ( given is 1025-43 and 
t = 18°-3 ; begin by cancelling the vacuum-correction, i.e.. substituting 1025'463 for the 
given S; then find that value x under 1025 which corresponds to t = 18 0, 3 (by inter- 
polation between 18° and 19°); i.e., compute 19*087 + 0*3 x 0*186 = 19-087 -1- 0‘056 = 
19-143. This is the x for 4 S 18 . 3 = 1025; the x for 1025-463 is greater by 0'463 x k 
where h means the value 
A(%) 
A(S) 
for t — 18°'3. 
According to the last column but one, we have Jc = 07245 ; diff. for 1° = 0"0017; 
hence k for 18°"3 = 07245 -I- 0"3 x 0"0017 = 0725. But 0725 x 0"463 = 0"336 ; 
hence the x sought is 19"143 + 0"336 = 19 '479 or rather 19*48, because the third decimal 
is purely accidental. 
To find the specific gravity 4 S at t° for a given x is, of course easy when the t is an 
integer, and the given x happens to stand somewhere in a line with that t. But as a rule 
this of course is not the case. Supposing we want the 4 S at 20° 7 for x = 18-60. The 
two x’s, under S = 1023 opposite t = 20° and 21° respectively come near to, and are less 
than, our number. By interpolation, we find that S 20 . 7 = 1023 for x= 18*006 + 0*7 x 0793 
= 18*141. The given x is by 0*459 greater, hence the S sought is greater than 1023 
by y x 0*459. Now h, by interpolation is 0*7289, hence AS = 0*459 -f- 0*729 = 
0*630, and 4 S 20 . 7 (meaning what I may call my specific gravity) is 1023*63. To reduce 
it to the vacuum deduct 0*03. But this is a troublesome calculation ; I shall therefore 
append a special table for finding Si 5 . 56 for a given x by mere inspection. From it any 
S, can be obtained by Table VII. 
