V O L U M E 2 3 , NO. 10, O C T O B E R 1 9 5 1
1499 culated from the values read from Figure 1.
Table 11. Calibration of Analytical Procedure (Using mixtures of strontium nitrate and calcium nitrate) Per Cent Strontium Nitrate Present Trial 1 2 3 4 5 6 AV.
Av.deviation
2.50
5.00
7.50
25.00
35.00
50.00
60.00
75.00
85.00
95.00
14.20 14.86 14.55 14.48 14.80 15.02
25.20 25.20 25.23 25.25 25.16
50.50 51.01 50.71 50.88 50.86 50.22
60.08 60.57 60.40 60.58
75.22 75.20 75.93 75.13 74.86 75.33
85.20 85.20 85.17 85.17 85.20
94.72 94.78 94.83 94.95
...
35.11 35.88 35.42 35.36 35.57 35.22
...
.. .. ..
14.65 -0.35
25.21 +0.21
35.43 +0.43
50.69 +0.69
60.41 +0.41
75.28
85.19 f0.19
94.82 -0.18
Per Cent Strontium Nitrate Found
1.75 1.20 1.64 1.17 1.25 1.20
4.09 3.90 3.92 4.04
.. ....
6.29 6.48 6.78 6.37 6.18 6.99
1.37 -1.13
3.99 -1.01
6.52 -0.98
LITERATURE CITED
15.00
ANALYSIS OF SAMPLES
For analysis of unknown samples the alkaline earth group is eeparated by standard methods which precipitate the metals as carbonates. Barium may be separated by the method of Beyer and Rieman ( 2 ) . The calcium and strontium are then separated as nitrates, by the method used for the calibration. T o the percentage of strontium nitrate found is added a correction cal-
.. .
...
+0.28
( 1 ) Barber, H. H., IND. Esa.
CHEM., ANAL. ED., 13, 572-3 (1941). (2) Beyer, G. L.* and Rieman? W., 111, Ibid., 19, 35-7 (1947). (3) Carbide and Carbon Chemicals Corp., Xew York.
“Cellosolve and Carbitol
Solvents,” 1947. (4) Kallmann, S., As.4~.CHEM., 20, 449-51 (1948); 21, 1145-6 (1949). (5) Kobe, K. A., and hiotsch, 11’. L., J.Phvs. Chem., to appear (1952). (6) Kobe, K. A , and Stewart, P. B., J . Am. Chern. Soc., 64, 1301-3 (1942). (7) Stewart, P. B., and Kobe, K. A., IXD.ENG.CHEir., . ~ K A L .ED., 14, 298-9 (1942). (8) Werner, H. m’.,hlitchell, J. L., Miller, J. TV.,and Von Oettinger. W. F., J . I d . Hug. Tox~coZ., 25, 157-63 (1943). RECEIVEDNovember 20, 1950.
Fuchsin-Sulfite Reagent in Colorimetric Determination of Formaldehyde LEON SEGAJ, Southern Regional Research Laboratory, New Orleans, La.
OFFPAUIR, Buckaloo, and Guthrie ( 2 ) have described for organic compounds including cellulose formals a colorimetric method of determining combined formaldehyde which depends on the development of color in Schiff’s reagent when formaldehyde is present. The reagent is standardized against known amounts of formaldehyde, and because it changes sensitivity on standing arid does not follow the Lambert-Beer law, a new standardization or IT-orkingcurve must be plotted each time the reagent is used. This method is simple t o use and was selected by the author for determining combined formaldehyde in cottons that had been treated with various formaldehyde solutions. When the reagent was prepared from basic fuchsin (rosaniline hydrochloride) in the manner described ( 2 ) , appreciable color varying from tan to red mas found t o remain after addition of hydrochloric acid, when it had been thought the color of the solution would he redured. I t was learned from one of the aut,hors of the method ( 1 )that, this had been observed by them but had heen overcome solely by use of a dyestuff of particular purity which, after addition of the acid, yielded a clear, slightly colored solution. For reliable analyt,ical result,s they recommended that only fuchsin which gave t.his color be used. Ten samples of basic fuchsin were tested, but none gave the rlesired color after addition of the acid. That the applicability of the procedure should be so limited by such a peculiarity of the rcagent did not seem reasonable, and a way was sought to use the fuchsin on hand. The color of the reagent was found to be removable h y decolorizing carbon (Xorit). This technique has been used for preparing Schiff’s aldehyde reagent for qualitative purposes (3,51, and Scott (4)satisfactorily accomplished the same thing using fuller’s earth. few minutes after addition of the acid, after the color had been lightened, about 1 gram of the decolorizing carbon was added to 500 ml. of the solution. The solution, after a vigorous shaking, was filtered through filter paper directly into the glasestoppered flask in which it was t o be stored. Comparison of the working curve of the clear and water-ivhite filtrate with that of the decolorized reagent prepared from the
“satisfactory” dyestuff referred to above showed t,hat, they were almost, identical. After about 1 month’s storage of the two reagents in the dark, the shapes of the two working curves r e r e still almost identical, although they had changed from the original, as was expected. This evidence indicated that the decolorized res the reagent prepared agent from stock fuchsin m-as as suit,able a from the particular dyestuff. Results of formaldehyde analyses carried out with the decolorized reagent checked very well with t h o v given by the recommended, but slightly colored, reagent. Sub,sequent use of the decolorized reagent has shown it to be satisfactory. Caution. Use of too much carbon will result in complete loss of sensitivity of the reagent-that is, no color whatever will develop in the presence of formaldehyde. Whether this is due to withdrawal from the solution of the sulfur dioside or of the rerlured dyestuff, by the carbon, was not investigated. Although Norit was used here, other ~imilarcarbons such as those employed by Tobie (6) should be suitable. In the original paper ( 2 ) sodium acid sulfite (Rodium bisulfite, NaHSO?), is specified for use in reducing the fuchsin. If, instead, sodium pyrosulfite ( Na&05, commonly called sodium metabisulfite and labeled sodium hisulfite by some manufacturers) is used, then t he weight of sodium acid sulfite called for must, be multiplied by the factor 0.908 in order t,o obtain that weight of pyi.o.eulfite which will release the proper amount, of d f u r dioside. The effect of sulfur dioxide content on the sensitivity of the reagent has been indicated by Tobie (6). LITERATURE CITED ( I ) Hoffpauir, ‘2, L., personal communication. (2) Hoffpauir, C. L., Buckaloo, G. W., and Guthrie, .J. D., IND.ENG. CHEY.,ANAL.ED.,15,605 (1943). ( 3 ) Mann and Saunders, “Practical Organic Chemistry,” 2nd ed., p. 379, London, Longmans. Green & Co.. 1936. (4) Scott, F. C., Analyst, 70, 374 (1945). (.i) Tobie, W. C., IND.ENG.CHEY..i l x . 4 ~Eo., . 14,405 (1942). RECEIVEDDecember 26, 1950. The mention of trade products does not imply their endorsement by ‘the Department of .4griculture over similar
products not mentioned.
