wool . 



1. Filter all samples through pyrex 

 Do not use paper filters. 



2. Pour duplicate 100-milliliter 

 portions of each sample into 250-milliliter 

 bottles and add approximately 0.1 gm. of 

 hydroxylamine hydrochloride with a small 

 spatula. 



3. Add 8 ml. of biquinoline reagent 

 to each sample and shake for 10 minutes on 

 the mechanical shaker. 



4. Remove from shaker and add enough 

 distilled water to fill the bottles. The 

 alcohol reagent will layer in the neck where 

 it can be easily removed. 



5. After at least 10 minutes, remove 

 3 ml. of the alcohol reagent with a 5-milli- 

 liter automatic pipette and dispense into 

 Fisher electrophotometer micro cells. 



6. Check the color density through 



a 525 B filter and convert to concentration 

 units by comparing with standard samples 

 that were analyzed with the regular samples. 



Biquinoline reagent: 



Dissolve 0.2 gm. of 2, 2 '-biqui- 

 noline in 1 liter of isoamyl alcohol 

 as follows: add all the biquinoline 

 to 100 ml. of alcohol; heat until 

 solution is complete; and then add 

 the remaining alcohol. 



Sulfide 



The method we used was similar to 

 that of Pomeroy (1941). This laboratory has 

 found no suitable means of stabilizing the 

 sulfide content of a sample and for this 

 reason all analyses are carried out immedi- 

 ately after collection. Aeration will 

 decrease the sulfide content of a sample. 

 Therefore, we treat all samples and stand- 

 ards so as to minimize exposure to air. 

 Standards were made from dilutions of Na2S- 

 9H2O. A moderately concentrated solution 

 was iodimetrically standardized and then 

 diluted to final working standards immedi- 

 ately before use. 



The determination is carried out as 

 follows: 



1. With a 50-milliliter graduated 

 cylinder, measure out 50-milliliter portions 



of the sample into 200-millimeter culture 

 tubes. 



2. With a 5-milliliter automatic 

 pipette, add 3 ml. of amine-sulfuric acid 

 test solution. Then with a 22-millil iter 

 automatic pipette, add 0.65 ml. of ferric 

 chloride reagent. 



3. Mix by closing vials with thumb 

 and inverting once or twice. 



4. Allow vials to stand for 10 min- 

 utes. Then, to each, add 11 ml. of ammonium 

 phosphate reagent and again mix. 



5. Allow vials to stand for an addi- 

 tional 5 minutes and check the color density 

 with a Fisher electrophotometer using 23- 

 milliliter cells and a 650 A filter. 



6. Convert from density to concen- 

 tration units by comparing with standard 

 samples analyzed with unknown samples. 



Reagents: 



a. Stock amine-sulfuric solu- 

 tion. Distill para-amino-dimethyl- 

 aniline in an all-glass apparatus in 

 which the air has been replaced with 

 nitrogen. Mix 50 ml. of concentrated 

 H2SO4 with 30 ml. of water and cool. 

 Add this to 20 gm. of the purified 

 amine, stirring until solution is 

 complete. Make up to 100 ml. with 

 water. This stock will discolor 

 somewhat on standing, but its useful- 

 ness will remain unimpaired. 



b. Amine-sulfuric acid test 

 solution. Dilute 10 ml. of the stock 

 amine-sulfuric acid solution with 990 

 ml. of 18N H2SO4. 



c. Ferric chloride solution. 

 Dissolve 100 gm. of FeCl3-6H20 in 

 enough water to make 100 ml. of 

 solution. 



d. Ammonium phosphate solution. 

 Dissolve 400 gm. of diammonium phos- 

 phate in enough water (805 ml.) to 

 make 1 liter of solution. 



Oxygen 



We used Winkler's (1888) method, 

 slightly modified, (Dean and Hawley 1947; 



