Chemical data 



Dissolved oxygen, pH, and some specific con- 

 ductance determinations were made in the field. 

 Other analyses were made in the laboratory at Ann 

 Arbor, Michigan. A citrate bottle was used in 1952 

 to keep samples for laboratory analyses. In 1953 

 water samples for laboratory analysis for each col- 

 lection were placed in four 4-ounce bottles--2 glass 

 and 2 polyethylene. One each of plastic and glass 

 was frozen. Water for total-phosphorous analysis 

 (unfrozen glass) was preserved with chloroform. 



Dissolved oxygen . --The unmodified Winkler 

 method was used. Samples were taken directly 

 from Nansen bottles and fixed immediately. 



£H. --Determinations were made with aHellige 

 color comparator. Samples were taken directly from 

 Nansen bottles and analyzed immediately. 



Total alkalinity . — Determinations were by elec- 

 trometric titration with a Beckman Model G pH meter. 

 A 100-ml sample was titrated with 0. 02n H2SO4 

 to the HCO3 endpoint (pH 4. 4). Results are given 

 in ppm of calcium carbonate. Samples collected in 

 citrate bottles were used for this analysis. 



Calcium and sodium . --A Beckman DU spectro- 

 photometer with a flame attachment using an oxya- 

 cetylene flame was employed for sodium (wave 

 length 589 mu, slit width 0. 2 mm, sensitivity 9) and 

 calcium (wave length 622 mu, slit width 0. 4 mm, 

 sensitivity 9) determinations. Water collected in 

 polyethylene bottles (unfrozen) was used. 



Magnesium. --A Fischer AC electrophotometer 

 (3 ml cell and 525 mu filter) was used for colorimetric 

 magnesium determination (American Public Health 

 Association 1946). A fresh solution of titian-yellow 

 was made up daily. A new standard curve was made 

 each day to give added accuracy. Unfrozen water 

 from polyethylene bottles was used. 



Silica. --Determinations were made by the mo- 

 lybdate colorimetric method (American Public 

 Health Association 1946) with a Fischer AC electro- 

 photometer (23 ml cell and 425 mu filter). Unfrozen 

 water stored in polyethylene bottles was used. 



Ammonia nitrogen. — The sample, previously 

 frozen in a polyethylene bottle, was thawed in run- 

 ning water and brought to room temperature. One 

 ml of Nessler reagent was added to 60 ml of the sam- 

 ple in a 150 ml beaker and mixed. After 1/2 hour, 

 color development was measured with a Fischer AC 

 electrophotometer (60 ml cell and 425 mu filter). 

 Ammonium chloride solution was used as a standard 

 (American Public Health Associates 1946). Tests 

 indicated that various interfering substances were not 

 present in sufficient quantities to make it necessary 

 to follow procedures for their removal (Ellis, Westfall, 

 and Ellis 1948). 



Total phosphorous. — Determinations were made 

 by a modification of the method developed by Harvey 

 (1948). A 50 ml portion of the water sample pre- 

 served with chloroform in a glass bottle was placed 

 in a 60 ml flask and dried in an ovenat 100° C. to 

 facilitate the acid-digestion process. After the ad- 

 dition of 0. 5 ml of 40-percent sulfuric acid, the 

 flask, covered with a 30 ml beaker, was placed in 

 an autoclave for 7 hours at 25 pounds pressure. The 

 sample was cooled to room temperatiue and brought up 

 to 25 ml with double-distilled water, and 1 drop of a 

 solution containing 0.25 gm of stannous chloride and 

 1 ml of concentrated hydrochloric acid in 10 ml of 

 double-distiUed water was added. Maximum color 

 development, taking approximately 5 minutes, was 

 measured by a Fischer AC electrophotometer (23 ml 

 cell and 650 mu filter). Usually 35 samples were 

 placed in the autoclave at one time, and a series of 

 standards was always included. Values for samples 

 in each batch were determined on the basis of the 

 standards run with them. Molybdate and stannous 

 chloride solutions were made up fresh each day. 



Specific conductance. --Resistance measurements 

 (ohms) were made with a glass dip-cell and an 

 Industrial Instruments Type RC-16B-1 conductivity 

 bridge. Values recorded for hydrographic stations are 

 from determinations made aboard the Cisco ; all others 

 were made in Ann Arbor on samples from polyethylene 

 bottles. Resistance was converted to specific conduct- 

 ance in mhos/cm x 10° at 18°C (^13) ^Y ^^ following 

 formula: 



>6 



^18 - 



10^ 



R t (1 t c A_t) 



11 



