672 PROCEEDINGS OF THE AMERICAN ACADEMY. 



pers. They were the so called " citrate of magnesia " bottles made 

 by the Whitall, Tatum Co. The water was often stored in these 

 bottles for several days before analyzing it. 



The temperature of the water was determined by a Negretti and 

 Zambra deep-sea thermometer, which was attached to the cable 

 carrying the water bottle and directly beneath it. This thermometer 

 had previously been compared with a thermometer standardized by 

 the Deutsche Physikalische Technische Reichsanstalt. 



The volumes of sea-water taken for analysis and the volumes of 

 silver nitrate solution required to react with them were measured in a 

 Knudsen pipette and a Knudsen burette respectively; both were made 

 by R. Goetze, Leipzig. The former is an ordinary pipette of about 

 25 c. c. capacity, provided with a three-way cock at the top. This 

 arrangement allows the liquid to pass beyond the cock when the 

 pipette is being filled; but upon turning the cock so that the body of 

 the pipette is in connection with the air through its third opening, the 

 pipette empties itself and the excess of liquid remains behind. Thus 

 an exact filling is always attained. The Knudsen burette also has a 

 three-way cock at the top, which is used in the same way. It is filled 

 through a side tube entering at the bottom. The lower part is grad- 

 uated in terms of the standard used in Knudsen's Tables.^ The 

 volume between the smallest graduation marks is about .05 c. c. and 

 the total capacity of the burette is about 42 c. c. The burette used in 

 this investigation was carefully standardized and the graduations were 

 found to be equal within the limit of accuracy of the readings. 



A silver nitrate solution, containing about 42 grams of the salt per 

 liter, was prepared and stored in a large bottle of brown glass. This 

 bottle, which was placed on a shelf several feet above the table, was 

 provided with a two-hole stopper, through one hole of which a glass 

 tubule extended from the bottom of the bottle to the inlet tube at the 

 bottom of the Knudsen burette. The other hole of the stopper was 

 kept closed except during the filling of the bottle. 



The solution was standardized as follows. A tube of standard 

 sea-water, obtained from the " Conseil International " at Copenhagen, 

 was opened and the Knudsen pipette was immediately filled from it. 

 The water was run from the pipette into a beaker, allowing one minute 

 for drainage, and three drops of a one percent sodium chromate 

 solution were added as indicator. Silver nitrate solution was then 



5 Knudsen, Martin: Hydrographical Tables etc. Copenhagen, G. E. C. 

 Gad, and London, Williams & Norgate. 1901. v + 63 pp. 



