CORRESPONDENCE "OXIDATION OF AMMONIA TO NITRIC ACID-A
DEMONSTRATION
Using the procedure as outlined by Haut for the generation of both oxygen and ammonia and with a pyrex tube filled with C.P. Baker's Copper Gauze which was An article entitled, "Oxidation of Ammonia to Nitric heated by means of a Meeker burner for the high temappeared perature required one noticed that a rather rapid genDemonstration"' by Arthur in the October, 1934 issue of the JOURNAL OF CHEMICAL eration of oxygen was necessary in order to get evidence of the brown fumes of nitrogen dioxide. The dioxide fumes did not appear in all cases. After placing a few cubic centimeters of water in the 500-cc. flask previous to the oxidation there was noticed during the course of the reactibn a blue coloration on the surface of the water and de6osited partially on the side of this flask. On testing for a nitrate, by means of the brown-ring test, no evidence of a nitrate having been formed was given; therefore, the blue compound was not copper nitrate. Upon slow air evaporation of this bluish green water solution bluish green crystals of the shape indicated in the photomicrograph remained. (See the figure.) A further attempt to identify these crystals after being air-dried for several days showed that they were quite soluble in dilute acid solutions, gave a basic reaction in water, and were not as soluble in water as in acid solution. On placing a few of these dried crystals in a small, clean, hard glass tube with an outlet tube running into a few cubic centimeters of Nessler's reagent and heatiug them, it was found that the Nessler's reagent indicated the presence of ammonia. EDUCATION, and your correspondent, after numerous The bluish green color was evidence enough that attempts, has discovered some interesting problems some volatile copper compound was formed. The tests above show some evidence or possibility that a complex connected therewith.
To the Editor DEAR SIR:
copper amine was formed, and yet the ammonia reaction with the Nessler's reaeent mav be evidence of onlv , occluded ammonia in the crystals. Only small amounts of these crystals were available and so no other tests were made. It should be noted, however, tbat the crystals were not definitely shaped in all cases, as in the photomiaograph, but in other cases they took on feathery appearances with modifications in-color from light green to copper-blue. In other words, the method as presented by using copper oxide as catalyst is not always entirely satisfactory in demonstrating the process of oxidation, because other complex reactions are involved, and is especially dangerous when a glass tube is used, for numerous explosions do take place in the tube. LEROYD. J O ~ S O N STORERCOLLEGE
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VIRGINIA HILRPER'S FERRY,WEST
A SIMPLE DETERMINATION OF THE EQUIVALENT WEIGHTS OF MERCURY, COPPER. AND ZINC WALFRIED SEEGER ,, - _,
St+srealschule.
is known from the synthesis of water.) By subtraction of that amount from the weight of zinc oxide the weight of zinc is found: 1 g. 0.197 g. = 0.803 g. Because the equivalent weight is tbat quantity which replaces one gram of hydrogen, or what is the same, binds eight grams of oxygen, the value for zinc can be calculated from the proportion:
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x:8 = 803:197 x = 33.6
The determination of the equivalent weight according to the described method requires little time, is economical of material, and is sufficiently exact. For control other methods of determination can be applied; for example: Zinc: measurement of the hydrogen liberated from acid by the metal; Copper: reduction of copper oxide with hydrogen; Mercury: quantitative decomposition of mercuric oxide by heat. P
MINUTES OF THE ANNUAL BUSINESS MEETING OF THE DIVISION OF CHEMICAL EDUCATION
Krems an der Dona", Germany (Austria)
The following report of the Treasurer was approved: PRINCIPLE
WEIGHED quantities of the metallic oxides are dissolved in excess hydrochloric acid and the surplus is titrated with normal alkali. From the resultant data the ratio of the weights of metal and oxygen, and consequently the equivalent weight of the metal, may be calculated. PROCEDURE
One gram of each metallic oxide (analytical grade) is dissolved in 40 ml. of normal hydrdhloric acid. For mercuric oxide 20 ml. is sufficient. Warming facilitates the dissolution of cupric oxide. With the aid of methyl orange as indicator the excess acid is titrated with normal alkali. The endpoint is the more easily recognized because at the same time the color changes, the formation of an hydroxide precipitate begins. In the case of copper the change of color is from violet to olive-green. EXAMPLE
One gram of ziuc oxide was treated with 40 ml. of normal hydrochloric acid. For the back-titration 15.4 ml. of normal potassium hydroxide was used; therefore, 24.6 ml. of normal hydrochloric acid was bound by the ziuc oxide. By definition 24.6 ml. of normal hydrochloric acid solution contains 24.6 mg. of hydrogen (H = 1, approximately). These 24.6 mg. of hydrogen bind an eightfold weight of oxygen, that is 197 mg. (The ratio
Cash on Hand March 25, 1939 Receipts from Dues Expenditures: Office of the ~hkirman Office of the Seeretam Lettcr lieads for ~ h & m a n Abstracts, naltirnore Meeting Deposited to Savings Account
$625.20 54.50
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$679.70 $ 25.00
25.00 10 29 3 00 ROO 89
Cash on Hand September 1, 1939
$366.78 $312.92
VIRGINIABARTOW.Treasurer
It was voted to appropriate thirty-five dollars toward the expenses incurred by Dr. Ethel L. French in connection with the questionnaire'and paper presented a t the current meeting. The Committee on the Naming and Scope of Committees reported approval of the proposal made a t the Baltimore meeting to establish a Committee on High School Chemistry. The Nominating Committee presented the following nominations for the next year, all of whom were duly elected to office: , M. V. M c G ~ LChainan N. W. RAKESTRAW, Vice-chairman P. H. FALL,Secretury R. L. EBEL,Executive Committee Member-at-Large NORRISW. RAKESTRAW, Secretary
