aniline was added 0.5 ml. of 0.5% p nitrobenzenediazonium fluoborate in the same solvent, 2 ml. of lOy0aqueous tetraethylammonium hydroxide, and enough solvent to make 100 ml. of solution. n’ith water as the solvent a wave-length maximum of 490 mp and a molar absorbance of 14,000 n-as obtained; with diniethylformaniidc as the solvent a wave-length maximum of 5 i O mp and a molar absorbance of 55,600 was obtained. The fourfold increase in int’ensity and the stahle brilliant purple color of the dimethylforinamide procedure would make it t8he procedure of choice. Similarly, data for the niicrodctcriiiination of many carbonyl and tlic,arbonyl compounds arc availahlt, ( 3 ) . Tlic carbonyl compounds were reacted with :ir>.ih>.tlrazinrs and the colors t h a t formid \vrre thcn reportrd in :iqucwis or alcoholic* alkalinc solutions. TIM,mow basic solvents would bc of grwtcir w l u r in this work, becaus? the :inions \\-oultl :ibsorb a t longcr \v:tve lengths anti with grratcr intcwsity. Tahlc I V affords some mamplcs. In somi’ ~ ‘ a the w w a k organic acids \\-ould ionizc n-c.nkly. if at all, in aqucous 01‘ :tlcoholic~nlkalinr solution; in the niorc 1xwic solvcnts ionization would takr plac’ca r c d i l y (Table J’), LITERATURE CITED
(1) Bradley, W.,Lwter, E., J . Chem. Soc. 1951, 2129 ( 2 ) Hnnot, C., Buli. SOC chim. Relges 66, 76 11957). ( 3 ) fieugerg, ’ C., Strauss, E., Arch. Riochern. 7 , 211 (1945). ( 4 ) Palkin, S., Wales, H., J . Am. Chem. SOC. 46, 1488 (1924). ( 5 ) Porter. C. C., . I s ~ LC.H E X 27, 805 (1955).
RECEIVED for review AIarch 19, 1959. Accepted October 1, 1959.
Table IV.
Absorption Spectra of W e a k Organic Acids in Neutral and Alkaline Dimethylformamide and A!kaline Alcohol
Compound Phenol
275(1.8) 281 ( 1 . 5 ) 298 ( 5 . 4 0 ) 299 ( i 4 , o j ~ 338 (27.0)
1-Naphthol
4Kitro-N-perfluorobutyr ylaniline 4Trifluoroacetylaminoazobenzene
1-hnthrol 2-Hydroxyanthraquinone Isatin
280 ( 2 . 0 ) 290 (2.03) 836 (7.50) 358 (12 7 ) 375 (17.7)
310 ( 2 0 ) 356 ( 5 .GO)
401 (20.7) 395s (14.0) 420 (15.6) 482 (3.95) .548 ( 5 . 3 ) 550 ( 0 . 71) 553 (48.0) 561 (5.90) 575 ( 6 5 . 8 ) 580 (72.0) 600 (5,401 GO5 (60.0) 667 ( 6 3 , O )
395Fs ( 4 .O ) d 4 4 (4.20) 375 ( 2 . 9 ) 482 (5.3) 419 (0.87) 513 (0.63) hcetophenone-4nitrophenylhydrazone 529 (21.0) 413 (30.4) 502 (5.60) 1-Hydroxyanthraquinone 402 i 5 . 5 ) Cinnamaldehyde-4-nitrophenylhydrazone 418 (44,0)c 554 (38.4) 1,3-Bis(4-nitropheny1)triazene 532 (56.8) 409 (35.6) 2-.4nilino-3-chloro-l,4naphthoquinone 563 (4.60) 482 (4.50) 4’-Nitro-4hydroxyazobenzene 510 (35.0) 385 (26.4) 4-Nitrobenzaldehyde-4nitrophenylhydra- 428 (42.2) 600 (41.8) zone 4-(4’-Nitro-1 ’-naphthy1azo)-1-naphthol G60 (35.4) 700 (73 . O ) 480 (20.0) a Dimethylformamide containing 2y0 of 10% aqucous tetraethylammonium hydroxide. b 95% ethyl alcohol containing 2c!4 of 10% aqueous tetraethylammonium hydroxide. c In 9570 ethyl alcohol. d Fs, fine structure. Table V.
Per Cent Ionization of Weak Acids in Basic Solvents“
Weak Acid
Per Cent Ionizntionb ~ _ _ Dimethyl12-Methoxyformamide Acetone Butanol ethanol 3Iethanol 100
100
100
100
100
100
100
100
100
20
phenylhydrazone
100
100
100
100
5
nitrophenylhydrazone
100
100
100
phenylhydrazone
100
100
10
1,3-Di-p-nitrophenyltriazene 4-Nitrobenzaldehyde-4nitro-
phenylhydrazone
3-Nitrobenzaldehyde-4-nitro-
4Diethylaminobenzaldehyde-42-Kitrobenzaldehyde-2-ni tro-
-50
0 0
0
4TSitrobenzaldehyde-2-nitro-
phenylhydrazone 100 7 00 1 0 4-Phenylazodiphenylamine 1o o c 35 0 0 4Phenylazoaniline -40 0 0 0 a All solutions contain 2% of 10% tetraethylammonium hydroxide in rater. * Determined by ultraviolet visible absorption spectroscopy. c With addition of 3% water, ionization was 80%.
0 0 0
Interaction of Beta Particles with Matter Analysis of Hydrocarbons by Beta-Ray Backscattering PETER R. GRAY, DONALD H. CLAREY, and WILLIAM H. BEAMER Radiochemistry Laboratory, The Dow Chemical Co., Midland, Mich.
,The determination of carbon-hydrogen ratios of hydrocarbons b y @-ray backscattering i s nondestructive, rapid, simple, and accurate. Mass density has a small effect on the P-ray backscatter intensity and the sample density must b e known to 0.01 gram per cc. The standard deviation in the analysis of 13 hydrocarbons b y pr a y backscattering i s less than 0.0370.
Mixtures of liquid hydrocarbons and solutions of solid hydrocarbons in hydrocarbon solvents are likewise analyzed to the same precision.
T
detcmiination of carbon-hydrogcn ratios of hydrocarbons by P-ray transmission or absorption techniques requires a precise measurement of the density of the sample 1‘4, 9). HE
I n atltlitioii, ttmpcraturc, control of thc sainple is ncccssai’y to maintain the drni;it\. constant tluiing the analysis. Carhon-hydrogc’n ratios of hytlrocarbons can he obtainctl also hy a d(>termination of thrir ?-ray backscattrring intensitirs. V l i e n h t a particlcms strike mattrr, some are “rc~fl~&d”hack in the direction tliq. came from The intensity of thcw backscattcwtl c~lccVOL. 3 1, NO. 12, DECEMBER 1959
2065
trons has bern known for some time to be dependent upon the atomic number of the scatterer (1, 5 ) , but not until recently has a systematic treatment of pray lnckscattering shown some of the regularities and potentialities of the phenomenon. These studies, by R. H. hIuller (7') and D. G. Muller (6),stressed tlic analytical implications of the method. The present investigations, on the other hand. are concerned with the analytical applications. Analysis by p-ray backscattering techniques has a distinct advantage over the determination of carbon-hydrogen ratios by transmission or absorption techniques. I n backscattering, density of the samples has only a small effrct on the intensity of the backscattered radiation, believed to be due to geometrical considerations, and must be known only roughly, whereas the densitj. of the sample is a first-order effect in transmission, having a greater cffect on the intensity of the transmitted p-rays than does the carbon-hydrogen ratio itself. EXPERIMENTAL
Apparatus. T h e p-rays incident on t h e hydrocarbon sample come from a source (20-millicurie strontium-90yttrium-90) mounted on t h e axis of a cylindrical ionization chamber detector (see Figure 1). The radiation is directed away from the detector windox so only scattered radiation can reach the chamber. T h e 20millicurie strontium-90-yttrium-90 Dra.y source is a small stainless steel capsule, '/4 inch in diameter and inch long ivith a n active spot 0.170 inch in diameter. The hermetically sealed source has a thin stainless steel window, 0.003 to 0.005 inch thick. The source is mounted in a brass holder attached to the ionization chamber. The source and source mount mask less than 5y0 of the effective ionization chamber window area. The 5-inch-long ionization chamber has an inside diameter of 3 inches with a 0.002-inch stainless steel window. The chamher is filled with argon to a total pressure of 2 atm. The current developed in the ionizxtion chamber is amplified by a balanced two-tube clectronieter consisting of a 2.5 X 10'3-oli~nprecision resistor, a n 80-ppfarad capacitor, and two CK5886 electrometer tubes (see Figure 1). Any unhnlaiice in the output of the electrometer is niiiplified in a three-stage hnlaweti amplifier. The unbalance voltage is fcd back to the grid of one of the electromrt,rr tubes through the 2.5 x 101O-ohn~resistor, bringing the system back into balance. The feedback voltage is accurately nieasured by a poteiitionicter-recorder system and is a measurc' of the total hackscattered radiation rcaching the detector. The feedback voltage is used as one input of a modified 13roivn Electronik strip chart recorder. The input voltage is bucked by a potential supplied by a battery 2066
ANALYTICAL CHEMISTRY
Block
Diogrom a t
-
Circuitry
Figure 1. Schematic diagram of ray backscatter apparatus
0-
through a "Sensitivity Adjust" potentiometer and a set of two decade resistance dividers. The setting of the two decades in series obtains the first two significant figures of the voltage readings and the recorder supplies the last two significant figures. The sliden ire of the recorder is replaced by a 100ohm 10-turn precision potentiometer and has a voltage span of 100 mv. The zero (with respect to ground) of the bucking voltage is set by a separate battery aiid "Zero Adjust" potentiometer. This bucking voltage netviork is indicated in Figure 1 as "Range Selector .'I Zero drifts or sensitivity changes of the instrument are corrected or niinimized by measuring the backscatter intensity from tn o standard solid samples of different atomic number. Tlie two potentiometers. "Sensitivity Adjust" and "Zero Adjust." are set so that the scale readings from the standards are predetermined values. The instrument is calibrated nith the standards once or twice each day. K i t h the 2-second time constant Cpecificd, the statistical noise on the recorder is 2 4 scale divisions. This can be read to better than z t 2 division
