ABSTRACTS OF REPORTS OF FOREIGN INVESTIGATIONS. 



A rapid method for estimating nitrates in potable waters, 

 George Harrow {Jour. Chvm. ISoc, oU, j)p. ;^li0-3li.i). — Tlie author 

 son^lit to dcvist' a method for the estimation of nitrates which shouhl 

 be {IS ra])i(l as Nessk^r's test is for the determination of ammonia. The 

 metliod which he proposes depends on tlie conversion of nitric; acid into 

 nitrous acid by means of zinc dust, and the estimation of the nitrous 

 acid by the Griesa test (<^»'-napthylamine and sulphanilic acid). The test 

 reajjent is prepared by dissolving 1 fjram rr-iiaptliyhimine, 1 gram 

 sniplianilic acid, aiul li5 c. c. strong hydrocldoric acid, in about 200 c. c. of 

 distilled water, boiling with a small quantity of animal charcoal, filtering, 

 and then making up to 500 c. c. Standard solutions containing respec- 

 tively 1, 0.1, and 0.01 jiart of nitrogen as nitrates i)er 100,000 are made 

 by dissolving 0.721 gram of pure dry potassium nitrate in 1 liter of 

 water ( = 10 parts of nitrogen per 100,000 c. c), and diluting to the 

 required strength. 



The manner of making the test is described as'follows: Fifty c. c. of 

 each water to be tested (as many as four estimations may readily be 

 made at the same time) are placed in beakers of about 100 c. c. capac- 

 ity, and oO c. c. of each of the standard nitrate solutions in smaller 

 beakers. Ten c. c. of the test reagent «are added to each beaker, and 

 afterwards a small quantity of zinc dust (7-8 mg.). If nitrites are 

 l^resent in the water the pink color will api)ear without the addition 

 of zinc dust (Griess's test). If nitrates are present a more or less 

 intense pink color will appear on the addition of the zinc dust, and 

 after about 15 minutes the intensity of the color is compare<l with 

 that of the three standard nitrate solutions, the water being diluted 

 until its color corresponds with that of one of them. The author sug- 

 gests that perhaps the greatest accuracy may be secured by comparing 

 with the most dilute standard, in which case it ma^' frequently be 

 necessary to dilute the water a hundredfold. The necessary dilu- 

 tion being indicated by this preliminary test, the test is repeated 

 with diluted water, the comparison of color with that of the standard 

 chosen being made after 15 minutes in graduated Nesslerizing tubes 

 of equal caliber, as follows: "The standard solution occupying GO 

 c. c. in one cylinder, the water tested is run into the other until the 

 depth of the color appears to be equal. A reading is then made of the 

 quantity necessary. Say 45 c. c. were employed: then 45 : GO : : 0.1 : r 

 (=0.133), and sui)posing the water to have been ten times diluted, 

 it would coutaiu 1.33 parts nitrogen as nitrates and nitrites [per 



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