ranging in concentration from about 0.08 to 0.4 gram per liter. Procedure for Resin. T a r e a 10ml. volumetric flask on analyt’ical balance. Transfer into it 3.5 to 4.0 grams of resin sample. Reweigh and calculate sample weight. Fill t’o mark with pyridine, stopper, and agitate vigorously. Fill cell with pyridine and scan. Refill and repeat scan. Read absorbance a t 3.08 microns and record average. This is background. Fill cell with’sample solution and scan. Repeat scan. Read absorbance at 3.08 microns and record average. Corrcct this absorbance reading for background and water (as determined by Karl Fisher method) giving net absorbance at 3.08 microns. Refer the net absorbance t,o calibration curve to ascertain grams hydroxyl in the sample and calculate equivalents of hydrosyl per 100 grams. RESULTS AND DISCUSSION
Table I records the results in duplicate for hydrosyl determination on qiu samples of Epi Rez 510 by both the infrared procedure and the diborane procedure. Precision. An indication of t h e reproducibilitv of the method and how i t compares with t h e diborane procedure may be obtained from an evamination of the above d a t a . T h e mean of the differences between ‘Trial 1 and 2 for t h e six samples by t h e infrared method is 0.0017 or 3.8Oj, of t h e mean of the series of 12 recorded
values. T h e range is 0.000 to 0.003. The mean of differences between Trial 1 and 2 for the same six samples by the diborane method is 0.0022 or 4.8% of the mean of the series of 12 recorded values. Based on Table I, the infrared method has the higher precision. Accuracy. T h e accuracy of t h e infrared method can not be established with certainty because epoxy resin of known hydroxyl content is unavailable either by synthesis or by certification from a recognized bureau or agency. However, a n indication of accuracy can be obtained by comparing results of the infrared method to results of the diborane method. T h e mean of the 12 recorded values by infrared is 0.0462 and by the diborane method the mean is 0.0449. Assuming the latter value to be the true value, the mean error of the infrared method is 0.0013 equivalents hydroxyl per 100 grams resin and the relative error is 2.9%. With haste it is pointed out that it is only assumed the diborane method value is a true value and that more correctly the figures of 0.0013 and 2.9% should be thought of as differences. Taking into account the wide divergence in concept, theory, equipment, and technique of the two methods, the agreement is considered escellent. A11 subsequent determinations in this laboratory have been made by the infrared procedure using technical personnel. At the time the determinations reported herein were conducted, the only
resin under test was resin with a weight per epoxide of 180-220. Resins of higher weight per epoxide values containing more equivalents of hydroxyl per 100 grams resin would require use of smaller sample size. For example a sample size of 0.65 f 0.02 gram would be in order for a resin with a weight per epoxide of 2000. ACKNOWLEDGMENT
The author acknowledges the work of V. L. Watson in development of this procedure. LITERATURE CITED
(1) Dannenberg, H., Division of Organic Coatings and Plastics Chemistry, 142nd Meeting, ACS, Atlantic City, N. J., September 1962. (2) Kabasakalian, P., Townley, E. R., Yudis, M. D., ANAL. CHEM.31, 375 (1959’r. \ - - - - ,
(3) Martin, F. E., Jay, R. R., Zbid., 34, 1007 (1962). ( 4 ) Illehlenbacher, 5’. C., “Organic Analysis,” T’ol. 1, pp. 2-65, J . Mitchell, Jr., ed.. Interscience. Sew York. 1953. ( 5 ) Sknmark, G . A , , Weiss, F. ‘I?, ANAL. CHEM.28, 1784 (1956). (6) Yalladas-Dubois, H., 13ulI. SOC.Chem., France 16, 604 (1949).
11,It.
AnAMs
Jones-Dabney Company Division of Devoe & Raynolds Co., Inc. Louisville 8, Ky. PERMISSION of the Jones-Dahney Co., Division of Devoe & Raynolds Co., Inc. to publish this paper, is acknowledged.
Determination of Peroxide by Automatic Colorimetry SIR: I n the study of the radiolysis of aqueous solut,ions it is necessary to determine the amount of hydrogen peroside formed a t very low radiation doses. Low doses are required to minimize the effect of secondary reactions. The large number of samples and low concentrations of peroside require a sensitive, rapid analytical method. We developed an automatic colorimetric method that is very suitable for this purpose. The method is applicable to nearly neutral solutions, gives good precision over a range of 5 p.p.b. to 8 p.p.m., and is sufficiently sensitive to determine the amount of peroside formed by < l o 4 rad in many systems. Automatic colorimetry has been applied to various determinations ( I , 4, 6, 7 ) and the analysis of very low concentrations of chloride, nitrate, nitrite, ammonia, and ferrous and ferric iron was the subject of a previous report from this laboratory ( 2 ) . The reaction adapted for the peroside analysis consists of the osidat>ion of the leuco
base of phenolphthalein by peroside in the presence of C U + ~ . The resultant phenolphthalein color is measured a t 534 mb. This reaction has been used as the basis for a qualitative test for peroyide ( 5 ) , but the instability of the color formed in the reaction makes quantitative determination difficult by ordinary manual methods. The automatic colorimeter system makes quantitative determination possible by precise proportioning and proper mixing of sample and reagents and by precise timing in the color development step.
Apparatus. All operations, from reagent additions t o absorbance measurements are performed automatically with a Technicon AutoAnalyeer manufactured by Technicon Instruments Corp., Chauncey, S . Y. Complete descriptions of this instrument are available in the literature ( I , S, 7 ) . Components of the .l utoXnalyzer used in the peroxide determinat,ion are tbe sampler, proportioning pump> mixing coils, colorimeter, range expander, and strip chart recorder. The flow diagram including the manifold €or the proportioning pump is shown in Figure 1 . RESULTS AND DISCUSSION
EXPERIMENTAL
REDUCED PHENOLPHTHALEIN. Dissolve 100 grams of sodium hydroxide in 200 ml. of distilled water and add 50 grams of zinc dust. Add 10 grams of phenolphthalein (C20Hlr04) and boil under reflux for 2 hour.: or until the solution is colorless. COPPERSULFATE.Dissolve 0.4 gram cf coppcr sulfate (CuSO4.5H&) in 1 liter of distilled water. Reagents.
This method has been applied in numerous determinations of pcroside in nearly neutral nitrate solutions. Concentrations as low as 5 p.p.b. were determined with good preciiion (relative standard deviation, 2.3oj,). Working curves were not linear but were quite reproducible over the range of concentrations of interest. Preckion data obtained are summarized in Tahle I . VOL. 36, NO. 8, JULY 1964
1689
F l a Rata
Table I.
Precision of Automated Peroxide Method No. of
Concri. 5 p.p.b. 100 p.p.b. 1 p.p.ni. 4 p.p.111.
Rel. std. dev., Yo 2.3 2.4 0.7 1.6
measurementa 15 20 20 13
Conditions for 5 p.p.b. to 8 p.p.m. H202
Table II.
Light path, mm. 15 15 10
Concwitration 5-10 P.P.b. 10-600 P.P.b. 50 p.p.t).-8 p.p.m.
Range expansion 10 4 1
Concentrations from 5 p.p.b. t o 8 p.p.ni. were determined simply by ch:inging the range expansion and path Icngth of the absorption cell. Con-
Phcmlphthalein
(0.012M)
Figure 1 .
0.32:
-Rnp
Flow diagram of automated peroxide method
centrations higher than 8 p.p.m. required dilution or manifold changes. Proper conditions for concentrations between 5 p.p.b. and 8 p.p.m. are shown in Table 11. Scouting tests showed that the method is applicable in heavy water with very little loss of sensitivity. Strong oxidants and complexing agents for peroxide would be expected to interfere.
(3) Collins, P. F., Diehl, H., Smith, L. F., Ibid., 31, 1862-7 (1959). ( 4 ) Ferrari, A , , Russo-Alesi, F. M., Kelley, J. M.,Ibid., pp. 1710-17. (5) “Handbuch der Analytischen Chemie,” R. Fresenius. G. Jonder. eds.. Vol. VIa. p. 333, Springer, Berlin, ’1940: (6) Lundgren, D. P., ANAL. CHEM.32, 824-8 (1960). (7) Skeggs, L. T., Am. J . Clin. Path. 2 8 , 114 (1957).
E. K . DUKES M. L. HYDER
( 1 ) Ann. N . Y . Acad. Sci. 87, 609-51
Savannah River Laboratory E. I. du Pont de Semours & Co. Aiken, S.c.
(1960). (2) Britt, R. D., Jr., ANAL. CHEM.34, 1728-31 (1962).
WORK under contract AT(07-2)-1 with the LT. S. Atomic Energy Commission.
LITERATURE CITED
Spectrophotometric Method for Determination ot Tetranitromethane in Solution and in Air SIR: The analytical procedure reported recently ‘ ( 8 ) for trinitromethyl compounds yielded only 90 to 95% of nitroform from tetranitromethane (TKM). This mas wrprising, for this is the isolable yield in the preparation of potassium nitroform from T N M with hydrogen peroxide and pota.;sium hydroxide. Apparently, in methanol, hydroperoxide ion attack5 both a nitro group and the carbon atom to give nitroform ion and carbonate ion a9 in water does hydioxide ion only ( 5 ):
+
C ( N O P ) ~ OOH- .--t [C(S02)3 . . . NO2 . C(NOz)3NOzC(N02)4
. . OOHI-
-+
+ Oz + H +
+
(1)
+ 600HcO3-’ + 4NOz-+
f 3Hz0 f 302
+
+ +
1690
+
(2)
+
ANALYTICAL CHEMISTRY
EXPERIMENTAL
T N M in Solution. Apparatus. All
T N M has been determined colorimetricrtlly by its reaction with benzidine (6), and by titrating the iodine liberated w h ~ nTKhf reacts with iodide ion ( 3 ) . lhillic, JLI:tc.hrth, and Maxwell ( I ) rc1l)oi.t a quantitative gasometric determination of ‘1’554in which the nitrogen ~~ro(luc.c~l by the reaction with hydraz i i i v i< incawred: 2 (’(XO?)4 S2HI 4KOH 21
