ANALYTICAL EDITION
February, 1946
.Ileasitrernent. Neirh 01 Iiiwsure by volume a quantity of sample containing 0.03 mg. or less of nitrite. Treatment. hlost samples in water analysis need no further treatment. The proper treatment of other materials depends on the naturc of the sample. Basic or acidic samples are neutralized with hydrochloric acid or sodium hydroxide. DESIRED CONSTITUENT. Separation. If interfering ions are present, they should be complexed or removed to within the perrnissiblc concentrations given in Table 111. Measurement. To the sample in a 50-ml. volumetric flask add I .O ml. of acidified 4-aminobenzenesulfonic acid reagent. (To preparc this reagent, completely dissolve 0.60 gram of 4 a m i n e henzenesulfonic acid in about 70 ml. of hot water, cool the solution, add 20 ml. of concentrated hydrochloric acid, dilute to 100 ml. nith water, and mix thoroughly.) hIix well. Allow a t least 3, and not more than 10, minutes for diazotization a t room temperature in diffuse light. Then add 1.0 ml. of l-aminonaphthalene hydrochloride reagent (0.60 gram of 1-aminonaphthalene hydrochloride and 1.0 ml. of concentrated hydrochloric acid diluted to 100 ml. with water) and buffer the system to a pH of 2.0 to 2.5 with sodium acetate. This requires about 1.0 ml. of filtered 2 0 JI sodium acetate solution. Dilute to bolume and mix well. After 10 minutes, measure the intensity of the reddish purple color by the usual means. All measurements should be made within 30 minutes. Spectrophotometric measurenients can be made a t 520 m+ A green filter, such as a Corning 30.401 of suitable thickness, is recommended for filter photomctcrs. Permanent standards for visual comparisons have been suggested (4). For minute amounts of nitrite, add the reagents according to the above procedure to 50 ml. of sample in a Nessler tube. The color developed is compared with a series of temporary or permanent standards.
99 LITERATURE CITED
(1) .kin. Public Health Assoc., “Standard rinalysis”, p. 46 (1936).
Method>
\\‘ater
rii
(2) Assoc. Official Agr. Chem., Official and Tentative hlctliods of Analysis, pp. 222, 527 (1940). (3) Bratton, A. C., Marshall, E. K., Jr., Babbitt, D.. r t ~ ~Hend drickson, A. R., J. Biol. Chem., 128,537 (1939). (4) Daaet, R., J. pharm. chim., 7, 113 (1928). ( 5 ) Diaz, J. M. G., Arch. SOC. biol., Montevideo, 10,304 (1942). (6) Germuth, F. G., IND. ENQ.CHEM.,ANAL.ED., 1, 28 (1929). (7) Holbourn, A. H. S., and Pattle, R. E., J . Lab. Clin. Me d.. 28. 1028 (1943). (8) Ilosvay, L., Bull. SOC. chim., [3] 2, 388 (1889). (9) Kershaw, N. F., and Chamberlain, N. S.,IND.ENG.C H E M . . ANAL.ED.,14, 313 (1942). (10) Liebhafsky, H. A,, and Winslow, E. H., Ibid.,11, 189 (1939). (11) Lunge, G., Z. angew. Chem., 2, 666 (1889). (12) Lunge, G., and Keane, C. A., “Technical Methods of Chc~ili~.al Analysis”, Vol. 111, p. 408, London, Gurney and Jackson 1931. (13) Mason, W. P., and Buswell, A. >‘ “Examination I,, of W a t e r ” . p. 50, New York, John Wiley & Sons, 1931. (14) Reindollar, \V. F., IND.ENQ. CHEY., . ~ N . A I , . ED., 12. (1940). (15) Shinn, M. B., Ibid., 13, 33 (1941). (16) Treadwell. F. P.. and Hall. W. T.. “Analytical Chemistry”, Vol. 1 1 , ’ ~ 306,’New . York,’ John Wiley & Sons, 1942. (17) U. S. Pharmacopoeia, p. 417 (1942). (18) Wallace, G. I., and Neave, S. L., J . Bact., 14, 377 (1927). .
I
ABBTRACTED from a thesis presented b y B. F. Rider t o t h e Graduate School of Purdue University in partial fulfillment of the requirements for the decree of master of science, Octoher, 1944.
Rapid Estimation of‘ Effect of Pressure upon Boiling Points of‘ Organic Compounds C A R L B O R D E N C A , Southern Research Institute, Birmingham, A l a . T IS frequently convenierit in laboratory distillations under reduced pressure to have at hand a means for estimating rapidly the boiling point of a substance a t pressures other than that bcing used. A special case IS finding the approximate boiling point at atmospheric pressure by extrapolation from a single boiling point value obtained a t some reduced pressure. Another useful application is in selecting in advance a suitable reduced pressure for distilling a compound whose boiling point at atmospheric pressure is known. In these cases, a high degree of accuracy is usually unnecessary, and the consideration of accuracy I S offset by the convenience of having a generally applicable procPS of calculation or extrapolation. Kumerous methods have been proposed for estimating boiling points a t reduced pressure or finding the vapor pressure of substances at various temperatures. One of the most useful is that of Cragoe ( I ) as modified by Hass and Xewtoii (4), which employs thc equation:
I
At = t’
-t
= .(273.1
9
+ t ) (2.8808 - log p )
+ 0.15 (2.8808 - log p )
(1)
where t’ = boiling point, O C. a t atmospheric pressure t = boiling point, O C. at pressure p (mm.) 4 = entropy of vaporization a t 760 mm. divided by 2.3 R Nass and Xewton have rnodificd Cragoe’s classification of compounds into eight groups according to their physical or structural relationship, and have established values for 4 for each group. However, calculation using this equation is rather cumbersome and time-consuming. The object of the present paper is to rcformulate the Hass-NeKton equation, and to derive graphs suitable for rapid interconversion and for use especially in the ordinary laboratory type of dist i l l c d o n . llliintion 1 may be rearrango11t o give:
t = t‘ (4
(9
+ 0.15 P) - 273.1 P + 1.15 P) 9 + 1.15 P
2)
where P = 2.8808 - log p . By the use of this equation and the entropy values giveri by Hass and Sewton ( 3 ) , graphs showing the relationshlp hctneen
Table I. Classification of Compounds According to Groups Compound Acetals Acetic acid Acetic anhydride Acetophenone Amines n-Amyl alcohol Anthracene hnthraquinone Benzaldehyde Benzene Benzoic acid Benzonitrile Benzophenone Benzoyl chloride Bromobenzene Butyric acid Camphor Caprylic acid Chloroanilines Chlorobenzene Cresols Coumarin Dibenzyl ketone Dimethyl oxalate Esters Ethers Ethylene glycol Ethylene oxide Formic acid Furfural Glycols Glycol diacetate Halogen derivati\res
Group 3 4
G 4
3
8 1 I 2
2
5 2
2 3
2
7 2
5 3 2 4
2
2 4
3
2
i 3 2
7
4
-
Same group as where X H
Compound Heptylic acid Hydrocarbons, sat. Hydrocarbons, unsat Isoamyl alcohol Isobutyl alcohol Isobutyric acid Isocaproic acid Lauric acid Laurylamine Irethy1 salicylate Myristic acid Naphthalene a- and 0-Naphthols Nitroalkaneu Nitrobenzene Nitrotoluenes Nitrotoluidines Allo-ocimene Octanols Oleic acid Phenanthrene Phenol Phthalio anhydride a- and 0-Pinenes Propionic acid n-Propyl alcohol Quinoline Sebacic acid Stearic acid Sulfides Valeric acid Water
Group 7 2 1
7
8 6 7
6 7 2
5 2 3 3
3 2 2
1
8 5
1
5 2 1 5 8 2 7 5 2 7 6
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 18, No. 2
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
