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Enrolment is proceeding at, and application should be made at once to ROYAL NAVAL DIVISION, 6, 7, 8, Old Bond Street, London, W. Phone.-REGENT 5515. GOD SAVE THE KING. CHEMICAL NEWS, Feb. 5, 1915 THE have continued the work during the year 1913-1914, and CHEMICAL NEWS. collected 43 samples, 36 of rain and 7 of snow, from VOL. CXI., No. 2880. NITROGEN AND CHLORINE IN RAIN AND SNOW. (SECOND PAPer). By WILLIAM K. KNOX. WIESNER (CHEMICAL NEWS, 1914, cix., 85) determined the nitrogen and chlorine in the different precipitations at Mount Vernon, Iowa, during the year 1912 1913. We Rainfall. October 4, 1913, to June 12, 1914. The samples were collected in porcelain-lined pans, 20 inches in diameter, in an open space near the centre of the village. The popula tion is about 2400 and there are no manufactures in the community. The snowfall during the period amounted to 11.5 inches, equivalent to o'95 inch of rain. The rainfall was 17'75 inches, a total of 18.7 inches of rain, which is above the normal for this section. The heaviest fall occurred on June 4, when the precipitation was 4'5 inches in a few hours. This contained a large amount of the various substances, as will be seen from the accompanying tables. The chlorine was quite constant, showing 10 6 parts per million. In calculating the results we considered that an inch of rainfall on an acre weighs 226 875 pounds. Date. October.. Chlorine. Nitrates. 0.30 10.6 0.32 0.0012 10.6 O'25 0'002 0 197 10.6 0.230 0'041 7 0.5 (rain and snow) 26-28 0.05 (rain and snow) 10.6 10.6 25 4'0 (snow) Trace On April 28 we made our first test for sulphate, and found it also in two subsequent precipitations. Later in the season no trace of sulphate was found, indicating that it comes from the sulphur in the coal. Our thanks are due to Dr. N. Knight for his assistance in this work. Cornell College, December 19, 1914. THE PERCHLORIC METHOD OF method has not been available to many chemists. Recently a 20 per cent solution at 3.00 dols. a kilo., a 30 per cent solution at 4.80 dols. a kilo,, and even stronger solutions of perchloric acid have been placed on the market. The quantity of perchloric acid necessary to combine with I grm. of potassium costs 3.8 cents. The cost of an equivalent amount of chloroplatinic acid is 4.90 dols. The cost of perchloric acid in the perchlorate method is not only lower than the cost of platinum in the chloroplatinate method, but is much lower than the cost of recovering the platinum. The precipitate KCIO4, is of constant com DETERMINING POTASSIUM AS APPLIED TO position, its solubility in 96 per cent alcohol containing WATER ANALYSIS. By CLARENCE SCHOLL. POTASSIUM is determined gravimetrically as potassium chloroplatinate (K2PtC16), as potassium cobaltinitrite (K2Co(NO2)6), and as potassium perchlorate (KCIO4). The potassium chloroplatinate method is most commonly used. It is accurate, but there are difficulties because of the solubility of the salt in alcohol, the non-uniformity of the precipitate, the loss by ignition, and the cost of material. The cost of chloroplatinic acid equivalent to I grm. of potassium in the precipitate, K2PtCl6, amounts to 4.90 dols. While this material can be recovered, the cost of recovery is considerable. The determination as potassium cobaltinitrite in its present form is not satisfactory (H. B. McDonnel, Bur. Chem. Bull. 162, 19, 1912). The results are unreliable. The potassium perchlorate method, more commonly called the Wense-Caspari method (W. Wense, Zeit. Angew. Chem., 1891, iv., 691; 1892, v., 233; R. Caspari, Ibid., 1893, vi., 68), has been applied to the analysis of fertilisers and similar material containing alkalis, alkaline earths, iron, aluminium, magnesium, and phosphates. The chief difficulty in this method has been the obtaining of the perchloric acid. The danger of preparing the pure acid, as was attempted, is very great. For this reason the 0.2 per cent HCIO4 is almost zero, and the loss by ignition is eliminated. The fertiliser chemists of Germany have tested the method (Landw. Ver. Sta., 1903, lix., 313; 1907, lxvii., 145), and have obtained such accurate results that they have placed it on an equal basis with the chloroplatinate method by adopting it as an official method (Fifth Internat. Congr. of Appl. Chem., 1903, i., 216; 1903, iv., 940). In this method the sulphates are precipitated in a slightly acid solution. This solution of chlorides is then treated with an excess of perchloric acid (1.5 times that required to combine with all bases present), and evaporated with constant stirring until white fumes appear. A small amount of water is then added, and again evaporated with stirrring. This is continued until all volatile acids are absent. The perchloric acid lost by volatilisation is replaced from time to time. The precipitate, KCIO4, obtained is washed with 95 per cent alcohol immediately before drying. The author has modified this method as follows:Precipitate the sulphates in a strong hydrochloric acid solution, avoiding a large excess of barium chloride. Evaporate the resulting solution with only a slight excess of perchloric acid without stirring. Dissolve the residue, and again evaporate with perchloric acid. Wash the precipitate only with alcohol containing o'2 per cent perchloric acid before drying. |