of chloroforin, transfer to a 50-ml. volumetric flask, a n d dilute t o t h e mark with chloroform. (The sample portion should contain no more t h a n 35 mg. of anthraquinone in t h e case of chlorinated naphthalene a n d no inore than 50 mg. in t h e case of inineral oil or chlorinated diphenyl.) 'rransfer 10.0-ml. portions of the sample to each of two 50-ml. volumetric flasks. Dilute one flask (flask A) to volume with the hydrochloric acid dilution and dilute the other (flask B) with the magncsiuni chloride dilution solution. Dcgas each solution. 2 . For the I-IC1-containing solution, drtermine the proper sensitivity setting of the polarograph so that a scale reading of betn-een 50 anti 80 divisions is obtained a t -0.4 volt. Using this srnsitivity obtain the reading a t -0.25 volt and then rim the entire curve betn-cen 0 and -0.8 volt. If a niaximum is found in the region of -0.2 to -0.4 volt, start again with a smaller .ample portion. 3. Using the sensitivity setting dctermincd in 2 , repeat 2 for the magntsium chloride-containing solution (flak l3). (Use the same aliauot as chosen in 2 . ) 4. Transfer aliquots (as chosen in 2 ) of the unstnbilized imareanant to two t50-ml. volumetric flasis. -To one add from a buret a portion of the standard :mthraquinone solution containing approximately the same amount of anthraquinone as the sample solution. This is flaqk C. Designate the other as flask D. Dilute both to volume with the hydrochloric acid diluting solution. Degas each solution. Measure each as directed in 2 , using the same sensitivity settings. 5 . Calculate the concentration of anthraquinone. I n the following equation the letter refers to the reading obtained for the corresponding solution c,orrectcd for the base reading.
diffusion current in the solution of the dielectric and comparison of this current with that obtained from a known amount of anthraquinone in the presence of the unstabilized impregnant. The current increases linearly with concentration. The presence of the unstabilized impregnant-Le., the mineral oil or chlorinated diphenyl or naphthalene without anthraquinone-is necessary because the diffusion current constant for anthraquinone in the pure solvent is a fern per cent greater than in the presence of the impregnant. This is presumably a viscosity effect. When determinations are to be made on several batches of the same impregnant, the same reference may be uijed so long as the sample size does not vary b y more than 25%, R I a ~ m aoccur in the polarogram TI ith ewessive concentrations of anthraquinone. Decreasing the sample size will elimin,zte the maxima. The function of the electrolytes is to shift the wave for anthraquinone so that materials not similarly affected by hydrogen ion concentration may be detected or their effects compensated for. A high base current in the acid solution should also appear in the magnrsium chloride solution, so that the effect is not measured. K i t h most instruments, the currents for each solution may be read and used simply as scale divisions. X Leeds & Korthrup Electrochemograph Type E with associated dropping mercury electrode was used in this work. The anthraquinone was of the purity used in production of the capacitors. The melting range was 286-7' C. a t ea. 1O per minute. Because of uncertainties inherent in using aged impregnant in
( A - B ) X mg. of anthraquinone in standard aliquot
% anthraquinone = ( C - D ) X grams of sample in sample aliquot X 10 DISCUSSION
Essentially the method comprises the measurement of the anthraquinone
a n y form of calibration procedure, only ten production line samples have been tested in this laboratory. Further,
because of lack of confidence in a n y known procedure for anthraquinone in these impregnants, no complrtely independent determinations were made. Instead, the possibility of any effect causing a nonlinear current-concentration response was excluded by determinations both by use of standards as described herein and by the standard addition technique. The results by the two techniques agreed within ea. 27,. rln electrolytic mechanism for the stabilization of dit3lectrics has been described (8). The data available in the literature lead to one genrral conclusion: The stabilization of direct current capacitors is a n electrolytic phenomenon and the materials which can be used as btabilizers must be easily reduced electrolytically. There are a few stabilizers which function by different mechanisms-Le.. fuller's earth by adsorption of degradation products ( 1 ) . From the evidence cited it can be predicted that except, for solubility problems and thc few materials which function by othcr mechanisms, any of the useful stabilizers for direct current capacitors can be determined in this system. Its usefulness has already been provcd for some other quinones, azo- and azo\ybenzme, and p-nitrodiphenyl. LITERATURE CITED
i l l Berberich. L. J.. Friedman., R.., Ind. ' Ens. Chem.40,11fj1918). (2) Edsberg, R. L., Eirhler, D., Garis, J. J., ANAL.CHEX 2 5 , TD8-800 (1953). (3) Garn, P. D., iinpitblished data. (4) Isshiki. T..Tach K.. Pharm. Bull. ( J a p a n )2,266-9 (1944). (5) Sauer, H. A,, 3IcLPnn. D. A., Egerton, L., Ind. Eng. Cheni 44,135-40 (1952). (6) Wawzonek, Stanley, Berkey, R., Blaha, E. IT.) Riinnrr, h l . E., J . Electrochem. SOC.103,4,56-9 (1956). RECEIVEDfor review October 21, 1959. Accepted October 3, 1060. Division of Analytical Chemistry, Becknian Award Symposium on Chemical Instrumentation Honoring Howard Cars, 135th Meeting, ACS, Boston, Itlass., .ipril 1959.
Determination of Water in 1,l -Dimethylhydrazine, Diethylenetriami ne, and Mixtures HOWARD G. STREIM,l EGERTON A.
BOYCE, and JOSEPH R. SMITH
Liquid Propellant Section, liquid Rocket Propulsion Laboratory, Picatinny Arsenal, Dover, N. J. Minute quantities of water in some mixtures of alkylhydrazine and alkaline amines used as rocket fuels have an effect upon their ignition and combustion with nitric acid oxidizers in rocket engines. This paper describes investigations leading to the develop-
ment of a near-infrared and a gasliquid chromatographic method for determining water in 1,l -dimethylhydrazine, diethylenetriamine, and a mixture of these compounds. The precision and accuracy of both methods are compared.
D
of water in alkylhydrazine and alkaline amines used as rocket fuels are not easily acETERMINATIONS
1
present address, Stauffer ~ l , ~ ~ i ~ ~
Co., Chauncey, N. Y. VOL. 33, NO. 1, JANUARY 1961
85
complished by the classical Karl Fischer method because of interfering side reactions. Neutralization of these strong amine bases with excess glacial acetic acid, prior to titration with Fischer reagent, results in nonreproducible t,nd points when the water content is lcss than 0.5 weight %. The determination of n ater in 1 l-dimethylhydrazine (UDMH) by a high frequency method appears t o be highly dependent upon the nature and amount of impurities in the sample (6). -4 differential near-infrared spectrophotometric method for the determination of water in hydrazines using the 1.9-micron absorption band of water has been reported (1). This procedure is capable of high precision, but the accuracy is w r y much dependent upon the preparation of a dry refrrence sample by fractionation.
125 ml ADDITION FUNNEL w t t h Equalizing Arm
Figure 1 . Liquid drying apparatus
~
-DRY
P
\I 1 1u1
LIQUID DRYING COLUMN I D 20mm x 6 0 0 m m long filled w i t h 4 A Molecular Sieves, 8 x 1 2 Beads
11
GAS DRYING COLUMN I D lOmm x 6 0 0 m m long tilled w i t h 4 A Molecular Sieves, E x 12 Beads
NEAR-INFRARED M E T H O D
GLASS W O O L
The near-infrared procedure utilizes a liquid drying column filled with Linde 4 il. Molecular Sieves for the purpose of removing water from the sample. The sample is subsequently used in the reference beam of the spectrophotometer. An absolute gasonietric method for determining water whicah depends upon the formation of hydrogen in the reaction between calcium hydride and water. CaH2 2Hs0 Ca(OH)2 2Hz t (j),was used to indicate the efficiency of the Molecular Sieve drying operation and the accuracy of the near-infrared procedure for low concentrations of water in the dirthylenetriamine (DETAL). This method mas unsuitable for deterniining water in 1,l-dimethylhydrazine because of a slow reaction between the calcium hydride and the 1,l-dimethylhydrazinc., causing gas evolution. The advantages of Molecular $' Lieve drying over fractionation are many. Among them are rapidity, efficiency, and specificity for rrnioving water when other impurities present are of larger molecular dimensions than that of n ater. A fractionated sample used as a refercmce can result in inaccuracies caused by the removal of impurities that may absorb radiation a t or near the 1.9micron water band. It then bccomes necessary to determine the effect of impurities upon the absorbance of water. Molecular Sieve drying eatentis the differential spectrophotometric method to other compounds that are difficult to dry by fractionation. Diethylenetriamine, a very hydroscopic compound that boils a t 208.7' C., is rasily dric.d in this manner. The major limitation plawd upon Molecular Sieve drying is the siac of the molecule from which watrr is to be removed. Compounds such as hydrazine, which approximate the molecular
+
86
e
-
ANALYTICAL CHEMISTRY
NITROGEN INLET
NEOPRENE TUBING GAS OUTLET-
+
rlinicnsioiis of water, arc absorbrd by the sirve n-ith the evolution of much lwat. I n grneral, compounds larger units are not a d s o r b d by than 5.0 4.0 -4.I\Iolcwlar Sieves. EXPERIMENTAL
Apparatus. The liquid drying cdumii usrd for preparing reference saiiiplcs for the differential spectrophotometric measurement is shoivn In Figure 1. Silica absorption cells (Beckman No. 2300-10-89) of 1-cni. Dath length were used in a Beckman %lode1 n K - 2 recording spectrophotometer equipped TYit'h a tungsten lamp source and lead sulfide detector. -4gloved dry box through which was passed a constant stream of dry nitrogen \\-as usrd for transferring samples into the reaction flask of the gasometric apparatus and the absorption cells. Reagent Preparation. Freshly prepared liquid drying colunins were conditioned by passing t'hrough them a i d disrarding a 300-nil. portion of the sample. This removed fine particles of Molecular Sieve which tended t o interfere viith the spectrophotometric ahsorption measurements. Oncc caonditioned, the column may be usrd for several detcrniinations. Each niatcrial in which the water was to be determined was passed through the drying column a t a rate of 1 to 1.5 1111. pcr minute. Solutions containing
: i c l t l d impurities were treated in a n iclmticd manner. Procedure. One hundred milliliters of each sample were dried and small portions \\-ere transferred into two matc~hctl absorption cells for u s r as the reference liquid and for citablishing t'he ze1.o point of the calibration cwi've. 1lie rcniaining ~ o l u n i e was uscd to prepare several solutions of kr1on.n watclr content 11y adding \\.cligh tv 1 (Iu a n t i t ies of wa t ~r t o 11-c,igli d lmrtions of thr dried sample. -4 spc~c~trophotometricrecording between 2.2 and 1 . i microns was obtained for each sample with the dried sumple in thc reference beam. Thc absorbance caorrcqonding t,o zero n-ater wis (stablishccl by having dry saniplts in both beams. Instrument sensitivitj- was adjusted t'o a value of 0.50 on thc tluodial so that the slit opening a t 2.2 microns \vas lcss than 2.0 mm. a t the start of the recording. The temperaturc was that of thP laboratory (25' i 1' C.). r .
RESULTS A N D DISCUSSION
-4bsorbance measurements n-erc t a k m from the peak of the 1.93-micron \ v a t u band and a base line was dran n through the shoulders of the band at 2.1 and 1.8 microns. Each value way corrected for the base line obtained with tliv dried m n p l e . .\bsorbance data for dirthylenrtrianiinc-water mixtures are prev n t e d in Table I. The absorbances w r o plotted as a function of the ncight
SAMPLE
R E t O ' l 3 E R S E N $ I T I V I T Y ATTENJATION-
0 02ml.l-I, O I M E ~ H Y L H Y D R A Z I N E 4 0 9 6 % H,O 4 8 9 6 % n.C,H$Cp
I \
L
1
3c
29
26
I 24
Figure 2.
22
I 20
I
I
I8
16
I 14 TlMElmini
I
I
I
io
I
I
I
12
8
6
4
2
-3 3
Chromatogram of 1 , l -dimethylhydrazine with water and internal standard
per ccnt of water for each series of solutions, which resulted in straight lines passing close to the origin. X line of regression calculated by the niethod of leakt squares for each series of measurenirnts fits the equation : ?,=a+bz
d i e r e y is the corrected absorbance, 5 is w i g h t per cent of water, and a and b are the intercept and slope, respectively. The values for a and b for each compound and the mixture studies arc given in Table 11,along with tlw standard deviation of a single nt~:isureiiieiit. Molecular Sieve Drying. Thr capavity and c,fficiency of a freshly prepared and Ponditioned Molecular Sieve drj-ing column were estimated by passiiig successive portions of dietliyleneti iamine containing a fixed amount of n-atrr through the column. nctpriiiiii:itioii of residual water inclicatc>tlthe capacity of the column is liniitcti n-lien approximately 3.0 grams of 1vatc.r have lieen absorbed. Efficiency of a frrshly prepared and conditioned tlrj-ing column is indicated by tlie fact that ssmplrs of diethylenetriaminr which originally contained 0.28 weight 7;n-ater werr reduced to 0.03 weight % water aftcr a single pass through the column. -1 second pass through the
same column reduced the water to 0.019 weight % rrater. Impurities. U p t o 10% b y weight of p-aminoethylpiperazine added to a sample of diethylenetriamine had no effect upon the near-infrared determination of water. T h e structure of t h e spectral trace between 2 . 2 and 1.7 microns and t h e absorbance at 1.93 microns was not altered by addition of this impuiity. If t h e Molecular Sieves had adsorbed even minute amounts of the p-aminoctliylpiperazine, a sizable change in tlie ncarinfrared spectra n ould have berm ohserved. Previous investigations indicated alcohols absorb slightly in tlir 1.9micron region of t h r spectrum ( 1 ) . Up to 5% by ncight of absolute methanol was added to samples of dirthyl-
Table
II.
enctrianiine. rp to 1% by w i g h t of absolute methanol had no effect upon the determination. but a t 5% by weight of absolute methanol. a change occurred in the spectral trace of the diethylenetriaminc in the wave length range cited. It appears that a significant Table I. Absorbance at 1.93 Microns for Diethylenetriamine-Water Mixtures in a 1-Crn. Cell AbsorbAbsorb-
Wt. ?o' H20 0 156: 0 0 0 0 0
219
256 462 464
585
ance
1
Wt. H2O 0 Ti7 0 813 1 060 1 246
3 2
1 352 1 480
X 100 6 4
8 11 18 17 23
0 0
ance
x 100 31 0 33 4 40 8 48 9 51 5 56 6
Least Squares Data for Absorbance vs. Water Concentration
Solution (CH,)zS?H, NH(C?H,iXHy)z Diethylenetriamine plus I ,I-dimethylhydrazine, 4 : 1 mixture
Path Ordinate Length, Intercept Slope Cm. a b 1 . 0 +0.003 0.480 1.0
t 0 . 0 0 8 0.380
1.0
-0.002 f-0.012
0.1
Range, 1T.t.
70
S.D., HzO k 0 . 0 0 4 0 . 1 to 1 . 2 f-0.007 0 . 1 t 0 1 . 5
0.419 d ~ 0 . 0 0 4 0 . 1 t o 2 . 0 0.0386 = t 0 . 0 0 4 1 to 15
VOL. 33, NO. 1, JANUARY 1961
87
quantity of absolute methanol a t the 570 level is thus adsorbed by the Molecular Sieves. This results in an apparent increase in the water concentration of the sample determined by the differential near-infrared method. GAS-LIQUID
CHROMATOGRAPHIC
Table 111.
Least Squares Data for Peak Height vs. Water and n-Butyl Alcohol Content
6.231 0.874 h"(CzHJHz),' H*O n-C4HgOH
a
A Perkin-Elmer Vapor
Fractometer, Model 154C, equipped with a thermistor detector block and a constant volume microdipper sample introduction system, x a s used. T h e column was constructed from 12 feet of l/r-inch diameter stainless steel tubing. Column Preparation. Sixty grams of Theed were dissolved in a quantity of acetone equivalent t o t h e bulk volume of 140 grams of 30- t o 60-mesh ANALYTICAL CHEMISTRY
-2.996 -1.532
Slope b
S.D.,, Mm.
K
19.543 22.976
0.408 0,308
1,176
27.134 29.584
0.058
1 090
0.581
Sample size, 50 ml.; sensitivity ratio 1 to 4. Sample size, 50 ml.; sensitivity ratio 1 to 2.
Johns-PIIanville Co. Chromosorb W. T h e Chromosorb TV was added to this solution and the mixture was gently stirred. T h e mixture was placed on a steam bath and stirred constantly until most of the solvent was evaForated. Then it mas transferred to B borosilicate glass baking dish and dried in an oven at 100" C. for 2 hours. The material was sieved and the 30- to 60-mesh fraction was retained for the column packing. The column was packed in a conventional manner b y vibrating small portions of the coated chromosorb into it. Glass wool plugs were placed in each end of the column, whirh was then bent to fit the space within the fractometer. Procedure. Three sets of standard solutions were prepared b y n-eighing knon-n amounts of water and n-butyl alcohol into 1,l-dimethylhydrazine, diethylenetriamine, and a 1 to 4 niivture of the two compounds. An effort wa? made t o keep t h e concentration of n-butyl alcohol close to t h a t of t h e viater. Samples, 50-p1., were injected by a
Table IV. Precision and Accuracy in Determining Small Amounis of Water in Some Amines
Sample 1,l-Dimethylhydrazine
EXPERIMENTAL
88
a, Mm.
METHOD
The physical separation of water from mixtures and its determination by gas chromatography, although an attractive scheme, have been delayed by the problem of peak distortions and the lack of suitable partitioning agents. Severe tailing of chromatographic peaks has been attributed to the nonideal adsorption of the sample components on the surface of the support; this effect may be minimized by using a solvent of similar structure to the solute ( 3 ) . I n this respect, Ar+V,LV'jN'tetrakis(2 - hydroxypropy1)ethylenediamine (Quadrol), has been used effectively for separating inorganic and organic bases rind water with a short column (4). $imilarly, use has been made of tetrahydroxyethylethylenediamine (Theed) with reasonably good separation of water from amine bases ( 2 ) . I n this work, the latter compound has been used as the stationary liquid phase supported on Chromosorb ITr. Many of the difficulties of injecting reproducible microliter quantities of viscous liquids such as diethylenetriamine into the chromatographic column have been avoided by using an internal standard technique. The addition of known quantities of n-butyl alcohol to samples of 1,1-dimethylhydrazine, diethylenetriamine, or mixtures results in the formation of a well-resolved and symmetrical butyl alcohol peak adjacent to that of the water, without interference or masking (Figure 2). A small difference between the response of the thermal conductivity detector for equal concentrations of water and n-butyl alcohol was observed. This difference is significant and must be taken into account when using an internal standard. The ratio of the peak heights of n-butyl alcohol and water, for equal weight concentrations of these compounds, yields an appropriate correction for the difference in detector response.
Apparatus.
Intercept
Solution
Diethylenetriamine
V7ater, Weight Per Cent PresDifferent Found ence 0.97 0.92 -0.05 2.00 2.09 f 0 . 0 9 2 . 4 7 2.56 +0.09 4.10 4.19 $0.09 4.80 4.74 -0.06 Std. dev. Sr0.087 0 . 9 8 1.06 +0.08 2.00 2.03 +0.03 3 . 8 1 3.87 S 0 . 0 6 4.65 4.51 -0.14 4.77
4.82
Std.dev. = 1 to 4 mixture, 1.11 1.18 UDMH, DETA 2.14 2.21 2.80 2.92 3.79 3.91 4.71 4.74 Std. dev. = I
+0.05 i0.091 +0.07 $0 .07
$0.12 +0.12 $0.03 0.099
microdipper into the injection block of the chromatograph. The column teniperature mas fixed a t 100" C. and the helium carrier gas flow rate was held to approximately 200 ml. per minute. Thia high flow rate was required in order to have elution times which w r e within reasonable limits. RESULTS AND DISCUSSION
Peak heights of the elution curves for water and n-butyl alcohol in each standard solution were measured in millimeters, and calibration curve5 for water and n-butyl alcohol in the two compounds and the 1 to 4 mixture were constructed by plotting peak height (millimeters) against concentration (weight per cent), and extrapolating each curve to zero mater and zero butyl alcohol concentration. The equations for each of these straight lines mere computed by the method of least squares, and the ratios of the slopes of the n-butyl alcohol to the water lines for each compound and the mixture were determined. These data are summarized in Table 111. .Ilso given in this table are the ordinate intercepts, a, and the slopes, b. for the equation ?/ = a bx, the standard deviation of any point along the lines of regression S.D.,,, and the ratio of the two slopes as indicated previously. The procedure indicated above serves to evaluate the correctior. required for the difference in thermal conductivity response for n-butyl alcohol and for water. With this accomplished, water in an unknown sample may be determined by solving the following equation :
+
Weight per cent HzO = (Cn-C4HgOH)(P H.B,o) XK P.H. (n-CdHgOH) where C,-C4HoOII = concentration of ?i-butyl alcohol (weight per cent added to unknown sample) P.H.H,o = height of water peak, millimeters P . H . n ~ , E ,= ~ ~height of butyl alcohol peak in millimeters
=
ratio of slopes, b, of n-butyl alcohol and water calibration curves
Table V.
Comparison of Near-Infrared and Gas Chromatographic Methods for Determining Water in a Mixture of Amines
Synthetic Sample The results of several determinations of added water in 1,l-dimethylhydrazinc, diethylenetriarnine, and a 1 t o 4 mixture of these compounds are shonn in Table IV. The standard deviation of this method is =tO.O9 weight % water in the range 1 to approximately 5% water. Comparison of Methods. Nearinfrared a n d gas chromatographic determinations of water were made on five prepared samples of a 1 t o 4 mixture of 1,I-dimethylhydrazine and diethylenetriamine. T h e results are compared in Table V, in which t h e experimental values represent a n average of three determinations performed on each sample. The precision of these determinations using the near-infrared method was h0.06 weight % water and for the gas chromatographic method i t was 10.1 weight % water (calculated as an average deviation). Thc increasing error of the nearinfrared procedure which occurs when thc TT ntcr content of the sample exceeds
1
2 3 4 5 6
Water Present, Wt. % ... 0.99 1.96 3 80 7.40 10.0
Water Found, Kt. 7 0 XIR-
Difference
n. 14
...
i.00
1.94 3 60 7 00
...
2% by weight, is to be expected. This error is the result of water loading on the Molecular Sieve drying column, and the decreasing efficiency of the column beyond the 3-gram water limit previously stated. A multiple column drying technique for the preparation of reference samples extends the accuracy of this method t o a much higher range of sample water content. I n a similar manner, experiment has shown that the chromatographic procedure is limited to samples in which the water docs not exceed 7% by weight. ACKNOWLEDGMENT
The authors express appreciation t o John D. Clark, Chief, Liquid Propel-
+0.01 -0.02 -0.20 -0 40
...
Water Found, Wt. %
GC
Difference
0.15 i 08 2.03 3 91 7.30 9.6
to. 07
+o. 09
$0.11 -0.10 -0.4
lant Section, for helpful discussions throughout this work. LITERATURE CITED
(1) Cordes, H. F., Tait, C. W., ANAL.
CHEU.29,485 (1957).
(2) Diamond, L. H., Food Machinery and Chemical Corp., private communication, Aug. 14, 1959. (3) Knight, H. S., ANAL. CHEM.30, 2030
(1958). (4) Pust, H. K., Moberg, X. L., Xishibayashi, 3f ., Division of Petroleum Chemistry, 135th Meeting, ACS, Boston, Mass., April 5-10, 1'359. (5) Rosenbaum, C. K., Walton, J. H., J . Am. Chem. SOC.52,3568 (1930). (6) Weaver, R. D., Whitnack, G. C., Gantz, E, St. C., ANAL. CHEM.28, 329 (1956). RECEIVED for review June 17, 1960. Accepted August 26, 1960.
Detection of p-Cresol in Spot Test Analysis FRITZ FEIGL laboratorio da Producjo Mineral, Minisferio do Agricultura, Rio de Janeiro, Brazil VINZENZ ANGER Forschungslaboratorium der Firma loba-Chemie, Vienna XIX, Austria Translated b y RALPH E. OESPER, University of Cincinnati
b A test for p-cresol is based on the formation of a blue color lake if the p-cresol i s coupled with diazotized p-nitroaniline, and the product i s then brought into contact with magnesium oxide in alkaline surroundings. This test will reveal 0.2 pg. of p-cresol. The isomeric 0 - and rn-cresols and phenol do not show this reaction. Cresylsulfuric acid, which i s readily cleaved by mineral acids, likewise can be detected by this procedure. Resorcinol, 1 -naphthol, chromotropic acid, H-acid malonamide, and pyrrole behave like p-cresol. The group necessary for lake formation i s indicated.
A
for isatin has been described ( 2 )in which a deep blue water-insoluble product is formed by the action of p-nitrophenylhydrazine on isatin to vield the hydrazone (I), which in turn
reacts with hlg-:! and OH- ions [also l\fg(OH)2or l\IgO]. This blue material is not a stoichiometrically defined compound, but rather a color lake in which there is a saltlike binding of the hydrazone to the surface of the hlg(OH)z or N g O TTithout production of a new phase ( 1 ) . Tlie requisite acidic groups will be contained in the aci form (IIa) and in the aci-nitro-.no1 form (IIb) of the hydrazone (I):
V\/
All previous experience, such as the observed behavior of alizarin, alizarinsulfonic acid, and 8-quinolinol, shows that only one acidic group is involved in the chemical adsorption of acidic compounds on oxides and hyclroxides. I n the case of color lakes, a n essential role is also played by the coordinative bonding between the metal atoms and other parts of the adsorbed material. Consequently it appeared doubtful
I
H
TEST
VOL. 33, NO, 1, JANUARY 1961
0
89
