V O L U M E 2 5 , NO. 8, A U G U S T 1 9 5 3 Table I.
Summary of Analytical Data
Average Millimoles MHz/100 G. 4.55 2.89 1.92 1.22 21.65 .50 3.09 2.66 1.91 2.66 2.75 3.99 3.13 4.95 4.25
Sample NO.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1269
Average Deviation 0.055 0.09 0.02 0.02 0.105 0.035 0.140 0.070 0.050 0.065
0.025 0.005 0.055 0.060 0.015
Av.
0.054
Millimoles MH,/100 grams
=
Precision, Parts/ 1000 12.1 31.1 10.4 16.4 42.0 21.2 45.3 26.3 26.2 24.4 9.1 1.3 17.6 12.1 3.6 19.9
PV 105
RT.w.2
0.13 ml. a t STP (0.14 nil. a t usual laboratory conditions) to be substracted from (Lz- h)to obtain V. This blank value of -0.13 nil. is very close to the predicted value. The difference in volume between 4 grams of the salt and 10 ml. of solvent to that of their solution is +0.20 ml. as calculated from literature values of density. (The assumption is made that the density of the hydride mixture is equal to that of the pure salt.) The volume increase for vaporization of water into the dry reaction tube has been experimentally determined by attaching a dry reaction flask to the apparatus and noticing the volume change to be several tenths of a milliliter. The predicted correction is, therefore, close to the experimental blank, indicating that all factors have been considered. The pressure, P, is the barometric pressure corrected for the temperature of the mercury column and for the vapor pressure of water a t the temperature of the experiment, 2‘. Tables are available for these corrections.
(3)
where P = pressure, atmospheres V = volume of hydrogen, cc. R = gas constant, 82.05 cc. X atm./‘ K. T = temperature, K. w = sample weight z = valence of ,?.I R, T , and w may be substituted directly in Equation 3, but corrections must be made for P and V. Any temperature change during an analysis would lead to an erroneous result due to the thermal expansion or contraction of free air and hydrogen in the apparatus. If the temperature fluctuation is not large and has been accurately measured (tz t l ) , a correction can be made for it. using Charles’ law. There are two additional corrections to be made to ( 4 L1) to obtain the true volume of hydrogen evolved, V . The first is a correction t o be added for the change in volume of the inert salt (the major constituent of the sample) on solution. The second is a correction to be subtracted for the increase of volume due to the vaporization of water into the dry reaction flask. These two fairly significant effects, along with any minor effects (such as solubility of hydrogen in water), are corrected for with a series of blank determinations. These blank determinations are carried out using commercial potassium bromide, following the same procedure outlined. The authors have found a blank of about
-
-
DISCUSSION
An average precision of 20 parts per 1000 has been found for samples in the concentration range of 1 to 5 millimoles of MH, per 100 grams of sample as shown in Table I, all determinations being carried out in duplicate. Below 1 millimole per 100 grams, the precision is erratic and poor; above 5 milIimoIes there are indications that it is significantly better. It is also possible to determine the oxide or hydroxide impurity on the same sample by a subsequent titration of the solution after hydrolysis is complete, the amount of hydroxide corresponding to the hydride being deducted from the total titrated base. ACKNOWLEDGMENT
This work was carried out under a research contract supported by the Department of the Navy, Bureau of Ships. The authors are indebted to H. W. Kruschwitz and R. W. Bragdon for their assistance and advice. LITERAIURE CITED
(1) Krynitsky, J. A., Johnson, J. E., and Carhart, H. W., ASIL. CHEM., 20, 311 (1948). (2) Pepkowits, L. P., and Proud, E;. R., Ibid., 21, 1000 (1949). RECEIVED for review October 14, 1962. Accepted April 6, 1953. Presented before the Division of Analytical Chemistry at the 122nd XIeeting of the AMERICAN CHEXICALSOCIETY, Atlantic City, X. J.
Analysis of lacquer Thinners by Fluorescent Indicator Adsorption Method W. €1. ELLIS AND R . L. L E T O U R N E A C ’ Calgornia Research Corp.. Richmond, Calg.
c
-Y ONMERCIAL
lacquer thinners and those prepared according to
U. S. Government specifications ( 2 ) contain approximately
equal proportions of primary solvents and diluent hydrocarbons. The primary solvents are mixtures of alcohols, esters, and ketones; the hydrocarbons are aromatics and saturates boiling in the range 200’ to 300’ F. Existing procedures for the analysis of lacquer thinners involve several separate steps to determine t,he percentages of the various compound types present. A rapid, accurate adsorption method for the simultaneous, direct determination of aromatics, saturates, total hydrocarbons, and total oxygenated compounds is presented. PROCEDURE
The procedure for the analysis of lacquer thinners is identical to that previously published by Criddle and LeTourneau ( 1 ) for the analysis of hydrocarbon mixtures, with the substitution of a new dye and a new displacing agent. Alcohols were used as displacing agents in the analysis of hydrocarbons; they are
replaced by n-butylamine in the analysis of lacquer thinners, which already contain alcohols and other strongly adsorbed, oxygenated compounds. The new dye component, Rhodamine &‘B”Base (E. I. du Pont de Nemours & Co., Inc.), is added to the fluorescent indicator to mark the boundary between the oxygenated compounds and the n-butylamine. The Rhodamine “B” Base is prepared by dissolving 400 mg. of the solid in 10 ml. of 200-proof ethyl alcohol. Both dyes, the Rhodamine “B” Base and the hydrocarbon indicator described by Criddle and LeTourneau, are added to the sample in concentrations of 0.5 to 5 parts per thousand. Further minor modifications follow. Before adding the displacing agent, 20 mm. of dry gel is added to prevent the heat of adsorption from distilling sample out of the column. Considerable heat will be evolved when the butylamine is initially adsorbed. The additional gel is tamped gently with a glass rod to eliminate gas pockets that may have formed and to guarantee a tightly packed column.
1270
ANALYTICAL CHEMISTRY Table I.
Composition of Thinners Prepared to Test M e t h o d
Table 111. Analysis of Unusual Mixtures Known, %
Per Cent
Components Isopropyl alcohol Methyl ethyl ketone Methyl isobutyl ketone n-Butyl acetate n-Butyl alcohol Ethyl alcohol Ethyl acetate Methyl isobutyl carbinol n-Amyl acetate Aromatic hydrocarbons Saturated hydrocarbons
Ketone type 12 13 25
..
..
..
.. ..
..
37 13
Ester type
.. ..
..
25 8 7 10
.. ..
37 13
Mixed 10
U. 9. Govt. TT-T266a 10
15
30
..
.... , .
10
5 10 37 13
Arbitryy mixture
10
..
..
4
5
Priinary solvents 50 50 50 50 50
Aro-
matics 36.7 36.7 36.7 36.7 36.7
Saturates 13.3 13.3 13.3 13.3 13.3
Primary solrents 49.2 49.6 49.7 49.8 49.5
Aromatics 37.1 36.8 36.7 36.4 37.4
Saturate 3 24
..
.. ..
top of the aromatics to the top of the bright orange fluorescent dye marking the boundary of the butylamine-oxygenated compounds.
10 37 13
DISCUSSION
Table 11. Analysis of Thinners of K n o w n Composition Known, % Found. 5% Thinner 1 2 3
Isopropyl alcohol Aromatic 89 8 9 67
, .
20
37 13
Saturate 2 23
10 10
.. .. .. ..
Isopropyl alcohol Aromatic 90 8 10 67
‘
Found, %
Saturates 13.7 13.6 13.6 13.8 13.1
Care should be taken that the butylamine does not come in contact with the hands. The liquid can be conveniently added to the column from a wash bottle with a large opening. Two pounds per square inch gage air pressure is applied. Higher pressures result in poorer boundaries. After the fluorescent orange, top boundary of the sample has passed through approximately 25 cm. of the 3-mm. outside diameter glass tubing, the length of each section is measured. The leading, saturate section is colorless; the aromatic section is blue throughout. The aromatic-saturate boundary is taken as the point where the blue fluorescence first reaches its maximum intensity. The upper aromatic boundary is marked by a red or brown zone which is readily observed in ordinary light and which is included as a part of the aromatic portion. The oxygenated compounds are colorless and extend from the bromn section a t the
Four basic formula lacquer thinners and one arbitrary mixture were prepared and analyzed by this method. These basic formulas are typical of commercial thinners and represent most of the commonly used formulations. Table I shows the known composition of the thinners, and Table I1 gives the results of the analyses. To test the accuracy of the method a t low and high proportions of hydrocarbons and primary solvents, two mixtures of isopropyl alcohol and hydrocarbon were prepared and analyzed. Results are shoivn in Table 111. The experimental data indicate that the method described is entirely suitable and probably more accurate than previous methods for the analysis of lacquer thinners. The single adsorption step is rapid and gives direct determination of the principal constituents. The data at extreme concentrations of alcohol and hydrocarbons show that the method is applicable to samples over a wide range of composition and that it is also suitable for the analysis of oxygenated compound-hydrocarbon mixtures other than lacquer thinners. LITERATURE CITED (1) Criddle, D. W., a n d L e T o u r n e a u , R. L . , A s . 4 ~ C . H E M .23, 1620 11951). (2) Federal Specification TT-T-266a, “ T h i n n e r , Dope, a n d L a c q u e r , ” .Ipril 27, 1951.
RECEIVED for review January 28, 1953. Accepted May 15, 1953
Qualitative Test for Scandium Employing 2,5 -Dihydroxy-1,4-benzoquinone LEWIS POKRAS’ AND MARTIN ICILPATRICK Department of Chemistry, Illinois Institute of Technology, Chicago, I l l .
HE research program on the chemistry of the rare element Tscandium, recently pursued in this laboratory, was hampered by the absence of a generally useful qualitative test for the element. The literature, including current reference works on organic qualitative reagents, spot tests, and colorimetric methods, (1, 2, 7 , 8) refers to only one test of somewhat general applicability-the cochineal (8)test. However, even this reagent fails in media high in salt concentration; for example, in solutions containing residues from which scandium is to be recovered. It is in such systems that a good qualitative test ie most needed. A search for such a test was pursued throughout the course of the program, and involved study of the reagents listed below. Analogy with known reactions of ions somewhat related t o scandium chemically suggested that the reagents should have been applicable, but in every case results were unsatisfactory. The reagents examined were alizarin, ammonium thiocyanate, carminic acid, citric acid and sodium citrate, cochineal, cupferron, dimethylglyoxime, 2,4-dinitro-l-naphthol, diphenylthiocarbazone, 8-quinolino1, 8-hydroxyquinoline-5-sulfonic acid, morin, 11
Present address, J. T. Baker Chemical Co., Phillipsburg, iT.J.
nitroso-2-naphthol, 2-nitroso-1-naphthol, nitroso-R-salt (sodium salt of 2-naphthol-3,6-disulfonicacid), quinalizarin, salicylaldoxime, Schiff’s base of o-amino-phenylarsonic acid with salicylaldehyde, sodium alizarin sulfonate, sodium erythrosine, sodium p-nitroso phenolate, and tartaric acid and sodium tartrates. IYith a number of the above reagents initial results were promising, but on spectrophotometric study the color reactions observed were found to be due merely to the effect of the acidity of the scandium solutions on reagents which are acid-base indicators. Carminic acid, reported t o be the active agent in tincture of cochineal, gave essentially the same reactions as the latter reagent. The Schiff’s base referred to above, reported as a reagent for scandium by Kuznetsov ( 5 ) ,was found to be sensitive to high salt concentrations. In solutions 1 or 2 31 in sodium, potassium, and ammonium salts, this reagent gave a positive color test even in the absence of scandium. A recent paper by Frank ( 3 ) on metal complexes of 2,5-dihydroxy-1,Pbenzoquinone describes a precipitate formed by thorium, 1%-hichsuggests that this reagent might be applicable to the detection of scandium. The similarities between the thorium-
