counter and "record the reading in the V (ml.) 

 Digital Counter Reading column of the CCC- 

 Sheet. 



The proper technique for the analyst to follow 

 is to keep the eyes on the sample and not on the 

 digital counter because the end point (colorless 

 sohition) is the important step m the determi- 

 nation. Never reverse the rotation direction of 

 the delivery crank while the stopcock is in DE- 

 LIVEKY position. Always wipe the delivery 

 tip with a laboratory tissue between titrations. 



(4) Calculations of Dissolved Oxygen. — 

 After the samples are titrated, calculations for 

 dissolved O2 are performed as follows: 



Step 1. Compute V-Vb, Va-Vb, and V-Vb/ 

 V2-Vb; enter these values in the appropriate 

 columns of the log sheet. 



Table J-1. K Factor for (Micro) Winkler dissolved 

 oxygen calculations 



V3= Volume of KIO3 or KHdOsJj standard in ml. 

 (10 ml.) 



N = Normality of KIO3 or KHdO,)! standard (equiva- 

 lent/liter) (.OIN). 



E =5,598 ml. 02/Na2S203-5H20 equivalent. 



2 = Volume of sample displaced by reagents when 

 sample was treated (ml.) 



Step 2. From table J-1, K Factor for (Micro) 

 Winkler dissolved O2 oxygen calculations, deter- 

 mine the K Factor for the Vj, Flask Weighed 

 "to contain," and enter the value in the K Factor 

 column of the log sheet. 



Step 3. Calculate the dissolved O2 for each 

 sample, using the following formula : 



Where 0^=0.018 ml. of O2 added to the sample 

 with reagents when sample was treated. 



Step 4. Enter the calculated dissolved O2 in 

 the Dissolved Oxygen Os wl/L column of the 

 log sheet. 



Step 5. Calculate the average dissolved oxy- 

 gen of the two samples for each serial number, 

 and enter the value in tlie Average DissoVued 

 Oxygen O2 ml/L column. If the analysis results 

 for the replicate samples differ by more than 

 ±.01 ml./L, place a question mark in the aver- 

 age column and determine the accepted value 

 after comparing all sample results. After the 

 oxygen calculations are performed, they should 

 be checked by another person. File the CCC- 

 Sheet in the Oceanographic Station Folder 

 along with the A-Sheet and other data sheets 

 for the oceanographic station. 



J-17 Securing the Apparatus After Com- 

 pleting a Series of Titrations. — After a series 

 of samples have been titrated, or a day's work 

 has been finished, the apparatus must be secured. 

 Turn the stopcock to the fill position, and turn 

 the glass stopper in the reservoir to close the 

 vent. The microburette will remain clean longer 

 if it is kept filled when not in use. 



After the sui"vey is completed, drain the solu- 

 tion from the burette and flush with distilled 

 water. Never use the cleanijig solution to clean 

 the hurette. Disassemble the burette at the ball 

 socket joint to remove it from the titration box. 

 Store the digital counter assembly in its case, 

 and pack the reservoir, stopcock, mici'oburette 

 glass component in a well-padded storage case. 



If it is necessary to disassemble the digital 

 counter assembly, remove the coupling nut at 

 the glass-metal point. When assembling lu- 

 bricate the piston, gasket, and "O" rings with a 

 thin coat of silicone grease. 



J-12 



