SURFACE WATERS OF THE NORTH ATLANTIC OCEAN. 71 
furnished with a tap and finely drawn point, and with fiducial marks above and below 
the bulb, while the latter, also furnished with a very fine point, was divided to 
OH cub. centim. and read to '01 cub. centim. by means of a float. After a little 
practice the delivery of the burette could be easily regulated to '02 cub. centim. 
In each determination, the pipette was washed out twice with the sample about to be 
titrated, and it was always filled direct from the bottle containing the sample. 
The volume of the pipettes was ascertained by filling them repeatedly with care¬ 
fully tested distilled water at different temperatures. The following set of weighings 
give some idea of tlie accuracy attained in filling. Pipettes marked .’. and | — 
Weig 
ht of distilled water. 
Pipette. 
Temp. 
(!)■ 
(2). 
• 
70.3 
10-0113 
10-0080 
• 
7°-2 
10-0118 
10-0151 
8°-7 
— 
10-0117 
; 
8°-7 
10-0152 
10-0130 
12°-8 
10-0068 
100048 
12°-8 
10-0092 
10-0093 
These give for volume of pipette | , which was used for the winkle of the deter¬ 
minations— 
At 7°"2 C .10'02G cub. centims. 
8°-7 „ . . . . 10-027 „ 
12°-8 „ . . . . 10-025 „ 
showing that the volume of the pijoette is constant within limits of measurement 
throughout the whole range of temperature ordinarily experienced in the laboratory, 
and that the difterence of two fillings is not likely to exceed -004 cub. centim., a 
degree of accuracy greater than that required l)y the burette. The amount of silver 
solution ordinarily required was something over 25 cub. centims., measured to 
i -02 cub. centim., whereas the pipette gives Jh '001 X 2-5 = -01 cub. centim. 
The determinations of the first 250 samples were made in duplicate, with results as 
shown by the following half-dozen, taken at random from the laboratory book :— 
Sample. 
Cub. centims. 
1. 
of silver solution, 
2. 
11 
27-51 
27-51 
12 
25-91 
25-91 
13 
25-59 
25-58 
14 
24-88 
24-87 
15 
28-71 
28-72 
16 
27-56 
27-55 
