July 15, 1933
INDUSTRIAL AND ENGINEERING
the ratio axis at 0.84. This ratio is unsatisfactory for boilers operating at any pressure. The chart may also be used by those working with results in terms of grains per U. S. gallon without converting to parts per million, because the conversion factor from parts per million to grains per gallon is cancelled in the ratio. To aid in reading, however, the figures on both the total alkalinity and the sulfate scales should be divided by 10. For example, if sulfates were given as 30 grains per gallon (Example 2), and
CHEMISTRY
271
total alkalinity as 50 grains, the resulting ratio would be 0.84. ACKNOWLEDGMENT The author wishes to acknowledge the kind assistance of E. M. Ross for his help in certain calculations and preparations of the nomograph. RECEIVEDApril 6, 1933. Presented before the Division of Water, Sewage. and Sanitation Chemistry at the 85th Meeting of the American Chemical Society, Washington, D. C., March 26 to 31, 1933.
Identification of Amines as 3,5-Dinitrobenzoates C. A. BUEHLER,E. JANECURRIER,AND RAYLAWRENCE Department of Chemistry, University of Tennessee, Knoxville, Tenn.
T
HE amine salts of various sulfonic acids (8, 6) have
been recommended as derivatives for the identification of amines. This investigation concerns itself with the carboxylic acid-3,5-dinitrobenzoic acid-which appears to offer some advantages over the sulfonic acids as a reagent to be used in amine identification. I n brief, it may be stated that the 3,5-dinitrobenzoic acid is more readily available or more easily prepared; it combines with a great variety of aliphatic and aromatic amines to form salts which usually have low, sharp melting points; and the salts, as a rule, are easily prepared and purified. Although the amine salts of 3,5-dinitrobenzoic acid are not as stable as the acetyl or benzoyl derivatives of the amines, TABLE I.
their stability is such that recrystallization commonly leads to compounds having melting points sufficiently definite for identification purposes. Frequently the former are more easily prepared in a pure state than the latter. I n addition, while the acyl derivatives may be formed with primary and secondary amines, the 3,5-dinitrobenzoates are capable of being produced for all types of amines. Failures in the latter case appear to be due to the insufficient basicity of the amine. The results are summarized in Table I, which also contains for comparison the melting points of the corresponding ptoluene sulfonates. None of these compounds, with the exception of those of ammonia (3) and pyridine (7), appear to have been described.
3,5-DINITROBENZOATES O F
AMINES MBLTINQ
RE-
AMINE
CRYSTALLIZATIONB
MELTINQPOINT Obs. Corr.
c.
O
c.
COLOR
MOLARNEUTRAL EQUIVALENTNITROQEN RATIO Calcd. Found Calcd. Found
OF
P O I N T (6)
TOLUENE.
SULFONATE
Aniline 1 Light yellow 1:l 305.1 302.7 i3.77 13.65 238.4 1 o-Toluidine White 319.1 313.8 1:l 13.13 13.17 189.7-190.5 0a m-Toluidine Light yellow 319.1 1:l 317.5 13.20 13.17 174.6-176.1 1 p-Toluidine Orange 319.1 l!l 316.3 13.14 13.17 197.7-199.2 4-Amino-1 3-dimethylk)enzene 2 Light tan 333.1 1:l 12.52 339.0 12.61 180.4-181.3 o-Chloroadiline 1 339.6 Bright yellow 1:l 341.9 12.28 12.38 192.9-193.6 1 m-Chloroaniline Yellow 1:l 339.6 339.1 12.37 209.8-210.3 12.38 1 p-Chloroaniline Yellow 339.6 333.4 1:l 12.57 12.38 213-231 p-Bromoaniline 1 Yellow 1:l 384.0 381.2 10.94 214.2-234.2 10.94 +Nitroaniline Oil 21, m-Nitroaniline Orange 1:l 350.1 341.9 16.00 16.12 213.5-215.0 p-Nitroaniline l b Yellow 350.1 1: 1 34!. 6 232.2-234.7 16.00 16.09 p-Amjno henol 2 Yellow 1:l 13.09 12.88 252.1-253.6 1 o-Aminogenzoic acid Bright yellow 1:l 174.6 12.04 169.5 11.87 224.1-224.6 m-Aminobenzoic acid 1 Orange 174.6 1:l 12.04 176.9 12.01 255.9-256.5 2 p-Aminobenzoic acid Orange 176.1 174.6 1:l 12.04 11.97 238.6-241.6 Methylaniline 05 Li$;eyellow 319.1 1:l 315.0 13.17 13.12 Oil Dimethylaniline 1 2:l 272.1 272.6 12.85 Oil 12.66 Benzylaniiine 2e Faint yellow 1:l 395.2 389.9 148.3-148.8 10.63 10.71 Dibenzy!aniline Oil Acetanilide 1 Yellow 1:l 347.1 339.9 12.11 12.00 Diphenylamine Tri henylamine 1 6 o-Pien ylenediamine Yellow 320.1 1:l 17.70 17.50 267.3-268.8 m-Phenylenediamine 0 Yellow 320.1 1:l 17.50 17.35 296.8-297.8 2" p-Phenylenediamine Yellow 320.1 1:l 17.50 17.65 >340 2 a-Naphthylamine Red 355.1 1:l 11.82 11.83 248.4-249.91 @-Naphthylamine 1 Y$llOW 355.1 1:l 217.3-219.1 11.74 11.83 Benzidine 1 304.1 Light yellow 2:l 13.82 13.65 1 Pyridine L&teyellow 251.6 2:l f Quinoline lo 341.1 1:1 f Ammonia 0 Yellow 229.1 1:l 18.34 18.40 ......... Benzylamine 1 319.1 Yellow 1:l 13.17 13.12 184.5-185.6 Diethylamine 2 Light yellow 285.1 1:l 14.60 14.74 ......... Triethylamine Oa Light yellow 313.2 1:l 13.42 13.30 ......... 26 Urea 272.2 Light yellow 1:l 20.59 20.68 ......... Acetamide 05 241.6 Light yellow 2:l 14.49 14.50 ......... Benzamide 2 White 333.1 1:l 12.62 12.73 .......... Decomposition occurred on redissohing compound. a Recrystallized from mixture of alcohol and benzene b Recrystallized from cold benzene. f Nitrogen could not be determined by Kjeldahl method. 0 Determination was not possible because of intense color produced in solution. I Recryetallized from hot benzene. d Compound turned dark below melting point.
......... ......... .........
ANALYTICAL EDITION
218
EXPERIMENTAL I n general, to the Oeol Of each component Was dissolved, by heating if necessary, in 25 to 50 cc- of absolute alcohol, after which the two solutions were poured together on a watch glass t o crystallize. Purification was accomplished, unless otherwise stated in Table I, by recrystallization from absolute alcohol. The number of recrystalliZatiOnS necessary for Purity in each case is indicated in the second column of the table. The melting points on the completely &-dried salts were determined by the method of Mulliken (4). A thermometer calibrated by the Bureau of Standards was employed and stem corrections were applied in all cases to obtain the corrected melting points. The neutral equivalents were determined by the method of
Vol. 5, No. 4
Perkin and Sewell (6) which, for the salts of aliphatic amines, was modified in that the titration was continued until the end point with phenolphthalein remained after boiling for 5 minutes. For the nitrogen analyses, the modified Kjeldahl method used,
LITERATURE CITED (1)Dyer, J. Chem. Sot., 67, 811 (1895). (2) Forster and Keyworth, J . SOC. Chem. Ind., 43, 165T,299T,341T (1924);46, 20T, 397T (1927). (3) k h M a s t e r a n d Godlove, J. Am. Chem. Soc., 37, 2181 (1915). (4) Mulliken, “Identification of P u r e Organic Compounds,” Vol. I. p. 218,Wiley, 1904. ( 5 ) Noller a n d Liang, J. Am. Chem. SOC.,54,870 11932). (6) Perkin and Sewell, J.SOC.Chem. Ind.,42, 2 7 T (1923). (7) Pfeiffer, Ber., 47, 1580 (1914). R E ~ E IApril ~ ~ D 5 , 1933.
Amplified Ballistic Method for Measurement of Glass Electrode Electromotive Force ALLANHEMINGWAY AND E. L. ARNOW Laboratory of Physiological Chemistry, University of Minnesota Medical School, Minneapolis, Minn.
T
HE null instruments which have been used for balancing the voltage of a glass electrode system against the varied potential from a potentiometer are the vacuum tube ,voltmeter, the quadrant electrometer, and the recently suggested ballistic method of Morton (4). In the usual vacuum tube voltmeter method it is necessary to use a vacuum tube with a high grid resistance (1) which necessitates the use of a special vacuum tube (a, d, 5 ) . Because of the required shielding, the use of a quadrant electrometer is unsatisfactory. The authors have developed a circuit using the ballistic method, which has the advantages of the use of inexpensive vacuum tubes and elimination of electrostatic shielding, and will give the voltage of a glass electrode system in less than one minute to an accuracy of less than 0.5 mil& volt. A vacuum tube amplifier is used to amplify the ballistic throw which makes it possible to use a less sensitive galvanometer. The apparatus used is routine laboratory apparatus and the circuit is easily assembled.
RS
FIGURE1. DIAGRAM OF CIRCUIT 8,Leeds and Northrup single-contact short-circuit key CI 0.1 p farad (paper condenser) Cz’ 4 fi farads (paper condenser) C,: 2 p farads (paper condenser)
Ri, 0.1 megohm Rz, 0.5 megohm Ra 0.25 megohm R1’ 10 000 ohms RE:vaiiable galvanometer resistance
The circuit diagram is given in Figure 1. The condenser C1 is charged to a potential equal to the difference of POtential between the potentiometer P and the glass electrode system X . On tapping the key the condenser is discharged through the resistance R1, the discharge being amplified by
the vacuum tube circuit and indicated by the galvanometer
G. When the voltage of the potentiometer is equal and opposite to that of the glass electrode assembly, the ballistic throw is zero. The vacuum tubes used are either UX240 or UX222. The galvanometer is a Leeds and Northrup moving coil instrument, either a shunted type R having a sensitivity of 0.003 amperes per mm. deflection or the enclosed lamp and scale type with a sensitivity of 0.025 amperes per mm. By using a low grid resistance R1 it is possible to eliminate shielding and at the same time avoid the use of an extra condenser in the discharging circuit, as recommended by Morton (4). It is necessary to use a by-pass condenser of a high capacity at Cz; otherwise the ballistic throw becomes of a complex oscillating nature, making adjustment difficult. The condenser on standing acquires a charge from the paper dielectric, the so-called absorbed charge; hence it is necessary to neglect the first throw, if the condenser has stood for some time without being discharged. The use of a single stage of amplification resulted in increasing the throw six times. On introducing the second stage the ballistic throw was increased sixty times. A very satisfactory glass membrane is a bulb, 1 to 2 cm. in diameter, blown on the end of a tube of Corning H 015 glass of 5 mm. diameter. The inside of the bulb is filled with hydrochloric acid-potassium chloride buffer saturated with quinhydrone, and contact is made with this solution by means of bare platinum wire. Such an electrode maintains its calibration over a Iong period.
LITERSTURECITED (1) Elder, L. W., and Wright, W. H., Proc. Nat. Acad. Sci., 14, 936 (1928). (2) Greville, G. D . , and Maclagan, N. F., Trans. Faraday SOC.,27, 210 (1931). (3) Harrison, C. B., J. Chem. SOC.,1930, 2, 1528. (4) Morton, c,, Ibid., 1931, 2977. (5) Morton, J . S C ~Instruments, . 9, 289 (1932). R W E I V E April D 8, 1933.
