NITRITES AND NITRATES 283 
Nitrites. This determination is carried out on a 50 e.c. sample of 
the water in a Nessler tube. <A series of standards is also prepared by 
putting the following amounts of the standard solution of sodium nitrite 
in 50 c.c. Nessler tubes and diluting to the mark with nitrogen-free 
water: 0.0, 0.1, 0.2, 0.4, 0.7, 1.0, 14, 1.7, 2.0, and 2.5 ¢.c. add 1 ee. 
of sulphanilic acid and 1 ¢.c. of the naphthalamin acetate -or hydro- 
chloride solutions to each of the tubes including the sample. Mix and 
after standing for fifteen minutes compare with the standards. Whena 
50 c.c. sample is used the standard matched times 0.01 equals the parts 
per million of nitrites. 
The following reagents are required: 
1. Sulphanilic Aad Solutzon. Dissolve 8 gms. of the purest sulphan- 
ilic acid in 1 liter of 5N acetic acid (sp. gr. 1.04) or in 1000 c.c. of water 
containing 50 c.c. of concentrated hydrochloric acid. This will be 
practically a saturated solution. 
2. a-naphthylamin Acetaie or Hydrochloride. Dissolve 5 gms. of 
solid and naphthylamin in 1000 ¢.e. of 5N acetic acid or in 1000 c.c. of 
water containing 8 c.c. of concentrated hydrochloric acid. Filter 
through alundum or washed absorbent cotton. 
3. Stock Sodium Nitrite Solution. Dissolve 1.1 gms. silver nitrite 
in nitrite free water; precipitate the silver with sodium chloride solution 
and dilute the whole to a liter. 
4, Standard Sodium Nitrite Solutton. Dilute 100 c.c. of solution 
3 to 1 liter; then dilute 50 c.c. of this solution to a liter with nitrite free 
water, add 1 cc. chloroform, and preserve in a sterilized bottle. One 
c.c=0.0005 mg. nitrogen. 
Nitrates. (Reduction method.) Place 100 cc. of the sample 
in a casserole and, after adding 2 c.c. of the sodium hydroxide solution, 
reduce the volume by boiling to 20 c.c. Pour this into a 100 c.c. test 
tube (163 ecm.) along with two or three rinsings with nitrogen free 
water. Puta strip of aluminum foil and close the tube by means of a 
rubber stopper carrying a 5 m.m. glass tubing which will extend below 
the surface of distilled water in another tube. “The hydrogen is thus 
allowed to escape. The nitrogen which is lost in this procedure may be 
neglected. Allow this to stand over night (at least four hours). At the 
end of this time pour the contents of the tube into a distilling flask and 
dilute to 200-300 ¢.c. with nitrogen free water. Distill, collecting 
the distillate in Nessler tubes or in 200 c.c. flasks if the amount of nitrates 
is known to be high. If flasks are used to receive the distillate, an ali- 
quot portion must be Nesslerized. Nesslerization may be done directly 
when the supernatant liquid in the reduction tube is clear, 
