NSWC/WOL/TR 75-3 5 



Log wt / log wt STD-1 - log wt STD-2] 4*5 A h \ 



HMX =[" j\ HMX STD-1 l+log wt STD-2 



^A } 2 " A^ 



STD-1 STD-2 



A = the area of the respective spots. 



Ammonium Perchlorate 



The analytical procedure for the determination of ammonium 

 perchlorate is based on the use of a specific ion electrode which 

 develops a potential across a thin porous inert membrane. 



The potential measured is a function of perchlorate 

 concentration. A reference curve is prepared using a standard sea- 

 water to which is added known amount of perchlorate. Differences 

 in seawater samples may contribute to a small uncertainty in the 

 measurement, particularly at low concentrations. For clear seawater, 

 the method gives satisfactory results in the 1 ppm range, using a 

 research pH meter. 



4.3.2.3 Nitrate 



The nitrate electrode allows nitrate to be quickly and easily 

 determined in fresh waters. However, the nitrate electrode will not 

 operate in the presence of high levels of other ions, so it cannot 

 be used to measure nitrate in concentrated salt samples such as 

 seawater. 



Nitrate can be reduced to ammonia, allowing the ammonia electrode 

 to be used for nitrate analysis, without interference. The reduction 

 procedure is as follows: 



1. Place in a round-bottom flask 100 ml of (neutral) sample 

 and a magnetic stirring bar. To the sample, add 1 ml of concentrated 

 HC1 and about one-half gram of NaF . Stir vigorously. Add about 

 0.1 g of finely divided aluminum powder. Wait until the evolution 

 of hydrogen stops, then add 1 ml of 10 M NaOH. Pour the contents 

 into a beaker and measure the ammonia concentration by the ammonia 

 electrode (see 4.3.1.2). 



Samples which may already contain ammonia must be measured 

 first. The background level of ammonia is subtracted from the value 

 found after reduction. 



52 



