Vol. 17, No. 5
INDUSTRIAL A X D ENGINEERING CHEMISTRY
460
Table 11-Comparison of Caro-Brioux and Volumetric Methods Using Varying Amounts of AgN03 VOLUMETRIC METHOD CARO-BRIOUX Excess METHOD 0 . 2 5 K Per cent AgN03 Per cent SAMPLE cyanamide N Cc. cyanamide N REMARKS 1 Crude 18.09 1 18.03 18.03 2 18.07 CaCNz 18.12 19.32 2 19.32 19.28 2 Crude 6 19.30 19.30 CaCNz 19.32 65.03 6 65.02 65.21 3 HEN, 4 Crude CaCNz 3.73 1 3.65 3.67 +Kzs01 3 . 7 5 5 3.75 3.74 5 Crude CaCNz +KC1 2.36 1.71 1 . 7 1 4 . 9 1 7 dicyanodiamideN 1.~ 2 urea % N 6 Crude 7.34 3 6.46 6 44 4 8275dicyanodiamideN CaCNz 7.45 6 6.44 61431 2:24%urea N
...
..
This table shows that the results of the two methods are in very close agreement for samples of cyanamide which do not contain any dicyanodiamide or urea, but that they differ in the presence of these compounds. Moreover, the results are constant with varying amounts of ammoniacal silver nitrate. A comparison of the two methods was then made on a cyanamide extract and on the same extract to which dicyanodiamide and urea had been added. The composition of the latter solution was approximated as follows: cyanamide nitrogen, 15 per cent; dicyanodiamide nitrogen, 75 per cent; and urea nitrogen, 10 per cent. The results are shown in Table 111. Table 111-Determination of Cyanamide in Solutions Having a High Concentration of Cyanamide Derivatives (Figures in per cent) CYANAMIDE SOLUTION CONTAINING DICYANODIAMIDE A N D UREA CYANAMIDE SOLUTION ALONE Caro-Brioux Volumetric I-Caro-Brioux MethodVolumetric Kjeldahl N method method Ag titration method 22.98 22.43 19.68 19.22 19.25 23.82 21.87 19.64 19.15 19.17 22.36 23.25 19.64 19.22 19.22
These results again indicated that by the Caro-Brioux method of precipitation of silver cyanamide in the presence of dicyanodiamide some silver dicyanodiamide was also precipitated. Kappen3 found that his method was quantitative for pure cyanamide or calcium cyanamide not containing any other nitrogenous compounds and that dicyanodiamide interfered most. The volumetric method also gave results somewhat too high (0.4 per cent), and it was therefore concluded that reprecipitation was necessary. This was effected by dissolving the filtered and washed precipitate with dilute nitric acid and reprecipitating by the addition of ammonium hydroxide. Low results were occasionally obtained, however, owing to the combined solvent action of the ammonium nitrate in the presence of excess ammonia, previously pointed out by Grube and Kruger,4 and as shown by the following experiment: Cyanamide determinations were made by the volumetric method on 50-cc. aliquots of a crude calcium cyanamide extract to which 2 grams of ammonium nitrate were added. T o one sample the usual excess of a,mmonia was added while in another the cyanamide was precipitated without the addition of ammonia. The results are given in Table IV. Table IV
SAMPLECONTAINING No NH4NOa 2 grams NHnNOa 2 grams NHnN03
+ 1 cc. “,OH
Per cent cyanamide N
{;::E 20.52 20.70
That the solvent action of ammonium nitrate could be reduced by proper dilution was shown by an experiment in which 2 grams of ammonium nitrate were added to 25-cc.
aliquots of cyanamide solution. One solution was diluted with 100 cc. of water, another with 200 cc., and then 40 cc. of 0 1 N ammoniacal tilver nitrate were slowly added to each. The precipitate was filtered, dissolved, and titrated in the usual manner. The results are shown in Table V. Table V SAMPLE CONTAININQ No NH4NOa 2 grams NHdNOa and diluted with 100 cc. HzO 2 grams NHdNOs and diluted with 200 cc. H i 0
Mg
.
cyanamide N
I;,58.5
Is::
5
--.I
58.6 L3.7
Reprecipitation with the proper dilution was tried on the solution previously mentioned, containing 15 per cent of the nitrogen in the form of cyanamide, 10 per cent as urea, and 75 per cent as dicyanodiamide. The cyanamide determination checked very closely with the amount of cyanamide put in the solution, the potassium thiocyanate titration for cyanamide alone being 8.83 cc. and that for the solution containing dicyanodiamide and urea, 8.85 cc Method
A 2-gram sample of crude calcium cyanamide is extracted for 2 hours with 400 cc. of water in a shaking machine. -After filtering, 50-cc. aliquots are pipetted into 250-cc. beakers, 1 cc. concentrated ammonia is added, and ammoniacal silver nitrate run in with constant stirring from a buret a t such a rate that the drops can be counted very readily. If the sample is in solution, an aliquot equivalent to about 50 mg. nitrogen is taken for analysis. After standing for 15 minutes the precipitate is filtered off through a Gooch crucible containing an asbestos mat. The silver cyanamide precipitate is washed eight to ten times with distilled water, then dissolved with dilute nitric acid (approximately 1 N ) and titrated with standard thiocyanate solution in the presence of ferric alum indicator. I n the presence of a very large amount of dicyanodiamide it is necessary to redissolve the silver cyanamide precipitate in dilute nitric acid. This can easily be accomplished by running dilute nitric acid (not over 25 cc. normal acid) through the Gooch containing the silver cyanamide with the use of suction. The Gooch is well washed with distilled water. Reprecipitation is made by first diluting the solution to 150200 cc. and then adding a few cubic centimeters of ammoniacal silver nitrate and as much ammonia as is necessary to make the solution barely alkaline. The solution is well stirred, and after standing for at least 2 hours it is filtered, the precipitate washed, dissolved, and titrated with standard potassium thiocyanate as described above. If carbide is present in the sample it is necessary to kjeldah1 the silver cyanamide precipitate instead of titrating it. Japanese DyestufI Subsidy Continued-Accordin: to a cable received from Acting Commercial Attache Rhea, Tokyo, the Japanese Diet, before its adjournment on March 31, passed an act encouraging the Japanese dyestuffs industry. The act carries a subsidy not to exceed 1,000,000 yen per year, for six years (I yen =$0.416, a t the exchange prevailing April 2 ) , which is about one-half the former figure. The government has been guaranteeing an 8 per cent dividend on the stock of the Nippon Senryo Sciso Kaisha (Japan Dye Manufacturing Company), which has been subsidized to the extent of approximately 2,000,000 yen yer year. It is said that as many as sixty varieties of coloring materials have been manufactured, of which only about thirty-five have proved successful. There has been a tendency to import the more expensive and complicated dyes, and t o manufacture the cheaper and less difficult. Imports of dyes into Japan have been very heavy during the past year, and it has been impossible for domestic dyes to coinPete in the market on either a color or a price basis.
