ANALYTICAL EDITION
February, 1946
Table II. Comparison of Observed and Estimated Boiling Points Compound (Group) Boiling point Pressure 200 mm. 100 mm. 50 mm. 20 mm. 10 mm. 5 mm.
Coumarin
Acetophenone
Obs. (2) Est.
Obs. (4)Est.
iib
196 171 154 139
iii
196 170 152 136
154 133 115 94 81 69
155 135 118 96 81 70
Ethylene Glycol (7) Obs. Est. 158 140 125 105 92 80
158 139 124 105 91 79
101
ing point values for intermediate pressures may be obtained from the charts by interpolation. In general, the observed and estimated values have been found to agree satisfactorily. Representative results are shown in Table 11, which gives a comparison of estimated and observed values for typical compounds of different groups. The observed values given for ethylene glycol have been obtained by interpolation of values reported by de Forcrand ( 2 ) . ACKNOWLEDGMENT
the normal boiling point and the boiling point at reduced pressure for the eight groups of compounds have been constructed. The classification of the compounds and families of compounds given in Table I is adapted from the reference articles (3,4). I t is suggested that compounds not given in the table be classified in the group with compounds which they most closely resemble. In this connection, Cragoe (1) has pointed out that higher members of a series of compounds are usually in the same group, while the first members are generally in a different group. Boil-
The author wishes to thank H. B. Hms and R. F. Newton for their valuable comments. LITERATURE CITED
Cragoe, International Critical Tables, Vol. 111, p. 246, 1928. Forcrand, de, Cornpt. rend., 132, 688 (1901). Hass, J . Chem. Education, 13,490-3 (1936). Hass and Newton, "Handbook of Chemistry and Physics", p. 1731, 1944.
Small Amounts
Nephelometric Determination
OF
Sodium
F. K. LINDSAY, D.G. BRAITHWAITE, AND J. S. D'AMICO Z e o l i t e Research Laboratories, National Aluminate Corporation, Chicago,
Ill.
A rapid nephelometric method for determining small amounts of sodium salts in either liquids or solids is disclosed. A n alcoholic uranyl magnesium acetate reagent is employed, and comparative data are given to indicate the sensitivity of various alcoholic compo-
sitions. The method is accurate to approximately 1 grain per gallon of sodium salts, expressed as sodium chloride i n water analysis, and t o *0.003%, expressed as sodium oxide on solid samples. The method is particularly adaptable to routine analytical problems.
THE
Potassium chloride, lithium chloride, and sodium chloride solutions were prepared by dissolving the pure chemicals in triply distilled water.
advantages of employing alcoholic magnesium uranyl acetate reagents, or of incorporating alcohol in some manner before the precipitation of the sodium uranyl acetate triple salt, have been disclosed by several workers (1,2, 3 ) . The need for a very rapid, sensitive method for determining traces of sodium salts in a solid product suggested the advisability of trying to employ an alcoholic reagent in the development of a nephelometric procedure. By modifying the method of Caley, Brown, and Price ( I ) , a satisfactory procedure has been developed which is particularly useful for control analyses in the manufacture of solids with low sodium salt impurity specifications, but which may also be adapted to rapid estimation of sodium salt concentrations in liquids. APPARATUS
The photometer used in this investigation employed a Nalco blue photofilter, a General Electric light-sensitive cell (Catalog No. 88 X 565), a General Electric hiazda lamp No. 51 (6 to 8 volts), and an ammeter (Model 26) manufactured by Simpson Electric Co., Chicago, Ill. The specifications on the construction of the apparatus are: Distance from light source t o cell Distance from light source to filter Slit i n screen Length of path of light through solutions Thickness of cell walls
50 mm. 25 mm. 6 . 5 mm. wide X 16 mm. high 16 mm. 2 mm.
R E A G E N T AND S O L U T I O N S
ALCOHOLICAISGNESIUM U R A N Y L -4CETATE. T O 30 grams O f uranyl acetate dihydrate, 150 grams of magnesium acetate tetrahydrate, and 20 ml. of glacial acetic acid are added 500 ml. of alcohol and sufficient water to make up to 1 liter. The resultant is heated on the steam bath, with stirring, until the salts are dissolved. Care must be taken to lose as little solvent as possible during the solution step. The reagent is then stirred until cool, and filtwcd without further dilution into a brown glass bottle.
P R E L I M I N A R Y EXPERIMENTS
Although, after an extensive investigation on the value of precipitating the triple salt in a n alcoholic medium, Greene (9) came to the conclusion that the alcohol could not be incorporated into the reagent, the ease of controlling the precipitation medium when using only one reagent was especially appealing for the development of a nephelometric procedure where uniform crystal growth is imperative. In their earlier work, Caley, Brown, and Price ( 1 ) had successfuly employed an alcoholic reagent, and the authors' preliminary work was done using a slight modification of their reagent, but substituting the nephelometric procedure for their more complex and critical centrifugal estimation method. The study of reagents prepared using various alcohols was the initial step in the investigation of the method. I n Figure 1 are plotted representative transmittancy curves for reagents made from methanol, ethanol, isopropanol, a mixture of ethanol and
Table
I. Comparison of Sensitivit of Reagent Prepared from Methanol-Ethanor Mixtures 9 Volumes
h-aC1 Added Grains/ gal.
Ethanol
Ethanol, 1 Volume Methanol
0 2 5 10 15 20 25
91.9 88.0 83.0 77.0 72.0 69.5 67.0
91.0 87.0 83.0 78 0 73.0 69.5 67.5
8 Volumes
7 Volumes
2 Volumes
3 Volumes
Ethanol,
Methanol
Ethanol,
3Iethanol
6 Volumes Ethanol,
4 Volumes
1Iethanol
Methanol
90.0 88.5 84.0 80.0 76.5 71.0 69.5
90.0 90.0 90.0 88.0 84.0 80.0 75.0
Per cent transmittancy 91.5 86.5 82.5 77.0 73.0 70.0 67.5
91.0 88.0 83.0 77.0 73.0 69.5 67.0
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
102 A-
M PERCENT
8-
61.5
C-
W PERCENT METHANOL
W
PERCENT
PROCEDURE
6
ISOPROPANOL
PERCENT E T H A N O L
FLUS 7.5
PERCENT METHANOL
To 2 ml. of the solution to be tested in the test cell are added one drop of C.P. concentrated hydrochloric acid and 15 ml. of the alcoholic reagent. The two solutions are mixed by inverting five times, allowed to stand 5 minutes, and again mixed by inverting five times. After an additional 5-minute period of standing, the transmittancy is read and the sodium content determined by interpolation from a previously prepared standard transmittancy curve.
0
0
4
ETHANOL
Vol. 18, No. 2
RESULTS
FIGURE I E F F E C T OF VARIOUS
ON SENSITIVITY
92.5
87.5
90.0
Table
II.
NaCl Added Crains/gal.
:
5 10 15 20 25
35
82.5
85.0
80.0
77.5
Tu)
72.5
Stability and Reproducibility of Reagent Reagent Batch 1 91.0 87.0 83.5 79.0 73.0 69.5 67 5 63 0
Table 111.
Reagent Batch 2 Per cent lransmitlancy 91.5 87.0 83.0 78.0 74.0 69.5 68.0 63.0
OF
Reagent Batch 3 90.5 86.5 83.0 78.0 73.0 69.5 68.0 63.0
SoLwrIoNs. In Table 111 are tabulated the results obtained by adding known amounts of sodium ion as sodium chloride to natural raw waters. The accuracy of this rapid procedure is ALCOHOLS approximately 0.000015gram per cc. (1grain per REAGENT gallon) expressed in terms of sodium chloride. Relatively high concentrations of lithium and potassium ions do not affect the accuracy of the sodium determination. The results ob70.0 67.5 tained, using a standard 10 grains per gallon sodium chloride water to which was added varying amounts of lithium and potassium salts, arc shown in Table IV. SOLIDS.The procedure was developed primarily for analytical control in the manufacture of fluid cracking catalyst for the petroleum industry, It was found that nearly 100% of the sodium salts could be extracted from this siliceous material by boiling for 2 minutes in 1to 1hydrochloric acid.
Analysis of Solutions Water A 8.7 5.2 1.5 9.7
Rater B 37 0 30.0 7.9 10 7
NaCl NaCl Found Added Grains per gallon
NaCl Found
Total hardness a8 CaC03, grains per gallon Calcium a8 CaCOa, grains per gallon Sodium as NaC1, grains per gallon Silica, p.p.m. 5102 NaCl Added
To 10 grams of catalyst are added 20 ml. of 1 to 1 hydrochlorir acid, and the mixture is boiled exactly 2 minutes. After filtering, 10 ml. of alcoholic reagent are added to 2 ml. of filtrate, the two solutions mixed by inverting 5 times, allowed to stand 5 minutes, and mixed again by inverting 5 times, and the transmittancy is determined after an additional 5 minutes. In Table V, the results of this rapid method are compared with results obtained by the standard gravimetric procedure. The accuracy of the method can be considered to be o.00370 expressed as SanO.
Table
IV. Interference
Salt .4dded
10
None LiC12.5 LiCl 5 . 0 LiCl 1 0 . 0 LiCl 2 0 . 0 KCl 2 . 5 KCl 5 . 0 KCl 1 0 . 0 KC1 2 0 . 0
10
acetone, and a representative curve for methanol-ethanol mixtures. From these data, it is apparent that ethanol reagents, or ethanol reagents containing small quantities of methanol, are more sensitive than methanol or isopropanol reagents. Incorporating acetone, or increasing the alcohol content above 50% by volume, rendered the reagent less sensitive. The disadvantage of an increase in the alcohol content of the precipitation medium was apparently due to the enhanced crystal growth, which caused the precipitated sodium salt to settle very rapidly, thereby decreasing the accuracy of the transmittancy measurement. The possibility of using ethanol denatured with methanol was of special interest because of the relative ease of obtaining such mixtures. Table I shows the effect of increased methanol-ethanol ratios. Volume ratios of 3 to 7 can be tolerated before the detrimental influence of methanol is appreciable. Therefore, because of the availability of Formula 30 alcohol (10% methanol and 86% ethanol by volume), it was selected for the preparation of the reagent. Table I1 gives data illustrating the stability and reproducibility of this alcoholic reagent. Reagents 1, 2, and 3 were prepared about 5 days apart. The results are well within the limits of accuracy of the method.
of Potassium and Lithium
NaCl Present Grains/gal. 10 10 10 10 10 10 10
Table
% Transmittancy
Grains/gal. 88.0 88.0 88.0 87.5 88.0 87.5 88.0 88.0 88.0
V. Analysis of Solid Materials NazO
NazO Found
Sample
G ravimet ri 1%
%
%
1
0.0195 0.010 0,019 0.012
0.017 0,008 0.021 0,009
2 3 4
LITERATURE CITED
(1) Caley, E. R., Brown, C. T., and Price, H. P., IND.ENO.CHEM.. ASAL. ED.,6,202 (1934). (2) Greene, C.H., Ibid., 8,399 (1936). (3) Kahane, E.,Bull. 30c. chim., 47,382 (1930). PREEENTBD before the Division of Water, Sewage, and Sanitation at tbe 107th Meeting of the AMERICAK CHEUICAL SOCIETY, Cleveland, Ohio.
