INDUSTRIAL A N D ENGINEERING CHEMISTRY
606
Vol. 15, No. 9
aliquot of the distillate by dimedone precipitation according to Yoe and Reid (4). The data in Table I show that acetaldehyde or propionaldehyde did not interfere with the determination. @-Methylethylidene glucoside and cellulose, both of which produce aldehyde groups but no formaldehyde on acid hydrolysis, gave zero values. Good agreement was obtained between the analysis of cellulose formals by the colorimetric and dimedone gravimetric methods.
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.
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MG. FORMALDEHYDEIN 5 ML
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SOLUTION
FIGURE 1. TYPICAL WORKINGCURVE
In order to determine how small a sample it was practical to use, 5.840- and 6.207-mg. samples of trimethylene-d-mannitol were weighed on the microbalance, placed in 250-ml. volumetric flasks, and made to volume with 12 N sulfuric acid. The flasks were placed in a constant-temperature oven at 90' C. for 2 hours and cooled. Using 5-ml. aliquots and the above-described colorimetric procedure, values of 40.6 and 41.0 per cent formaldehyde were obtained. Samples of 0.062 and 0.127 mg., smaller than those commonly used for microanalysis, were weighed on the microbalance, placed in matched tubes of the colorimeter, and 5-ml. portions of 12 N sulfuric acid were added with a pipet. The stoppered tubes were heated at 90" C. for 2 hours and the color was developed, giving values of 39 and 40 per cent of formaldehyde, respectively, Considering the very small samples used, these values are in satisfactory agreement with the theoretical value of 41.29 per cent.
Acknowledgments hours and the transmission was determined. Spectrophotometric curves of the color developed indicated that filter 565, whose transmission limits are 550 to 585 mh, is the correct filter to use. I n the case of cellulose formals, about 0.1 gram of the material was accurately weighed and placed in 250-ml. glass-stoppered Erlenmeyer flasks. Exactly 100 ml. of 12 N sulfuric acid were added to each flask, and the flasks were placed in a constanttemperature oven at 90' C. for 2 hours or allowed to stand overnight at room temperature. Formaldehyde was determined on 5-ml. aliquots of the solution as described above. Solution of the sample was not necessary for correct results. Since cellulose formals of known com osition were not available, the results obtained by the methot described here were compared with the values determined by distilling the formaldehyde by the method of Wood (S),followed by determination of formaldehyde in an
The authors are indebted to the following members of this laboratory: James H. Kettering, Lamont Hagan, and J. David Reid for the cellulose formals; Richard E. Reeves for the /3-methylethylidene glucoside; and Robert T. O'Connor for the spectrophotometric curve of the color developed.
Literature Cited (1)
Blaedel, W. J., andBlacet, F.E., IND.ENG.CHEM.,ANAL.ED.,13,
449 (1941). (2) Haskins, W. T., Hann, R. M., and Hudson, C. S., J . Am. Chem. SOC.,64, 986 (1942); 65,67 (1943). (3) Wood, F. C., J . SOC.Chem. Ind., 52, 33T (1933). (4) Yoe, J. H., and Reid, L. C., IND.ENG.CHEM.,ANAL.ED., 13,238 (1941).
NOTE ON ANALYTICAL PROCEDURE Stability of the Nickelous-Ammonia Color System J. P. PVIEHLIG, Oregon State College, Corvallis, Ore.,
I
N DEVELOPING a colorimetric method for the determination of nickel in steel with ammonia Ayres and
Smith (1) found no change in the color of the system after 150 hours. I n a spectrophotometric study of this method the senior author of this paper found that there mas no evidence whatever of fading or other color change over a period of 4 weeks ( 2 ) . For the purpose of further study the six solutions which had been used in this test ( 2 ) , containing 100,200, 300, 500, 1000, and 1500 p. p. m. of nickel in 1.5 M ammonium hydroxide, were allowed to stand 55 weeks longer in glassstoppered Pyrex bottles in diffuse light. Spectral transmission curves were then made with the self-recording photoelectric spectrophotometer at Purdue University, and, when compared with the curves given b y the corresponding freshly prepared solutions, were found to be very similar. From the transmittancy at 582 mp, the wave length of maximum absorption for this system, the percentage error in the apparent concentration of nickel mas calculated ( 2 ) by use of the special color slide rule.
AND
R. E. KITSON, Purdue University, Lafayette, Ind.
The range of apparent change in concentration of the nickel was from -0.7 t o f7.1 per cent (average 3.0 per cent), thus showing that the color of the system is practically unchanged after 59 weeks. The percentage error is less in the more concentrated solutions ( 3 ) . Such marked stability makes possible the use of a series of permanent standards, which must, however, be kept tightly stoppered to prevent loss of ammonia. The action of ammonia on the glass is reduced to a minimum when Pyrex containers are used.
Acknowledgment The writers wish to thank M. G. Mellon of Purdue University, in whose laboratory this work was done, for the privilege of using the Purdue spectrophotometer.
Literature Cited (1) Ayres, G . H., and Smith, F., IND.ENQ.CHEM.,ANAL.ED., 11, 365 (1939). (2) Mehlig, J. P.,Ibid., 14, 289 (1942). (3) Ibid., 14, 903 (1942).
