IYDUSTRIAL AND ENGINEERING CHEMISTRY
306
grams of pale crepe rubber were milled on a 45 X 20 cm. mill, khrough which water a t 50" C. was circulated. The temperature of the rubber was approximately 70" C. during the milling. Samples were removed a t intervals for test. The consistency of the rubber was followed by means of both the pendulum plastometer and the parallel-plate plastometer (16). The results are shown in Table I. Several sets of data are shown with the pendulum instrument, in order to illustrate the degree of duplication. The samples run in the pendulum plastometer were in direct contact with the metal plates. TABLE11. ENERGY CONSUMPTION AND ELASTIC RECOVERY Material Rubber 100, mineral oil 30 Rubber 100, mineral rubber 60 Mineral rubber (0.5-00. sample) Tire tread stock Balata
Available Thickness Energy ReConsumed covered Recovery % Mna. % 24.8 0.53 41.4 37.5 0.41 32.8 5.6 68.0 0.07 67.0
57.3
4.03 0.54
322.0 42.1
The data obtained with the two instruments are directIy comparable only in regard to the elastic recovery. The pendulum instrument shows not only a much higher recovery, but a much greater difference between the extremes. The thickness index of the parallel-plate plastometer, while not indicating a quantitative energy relationship, has a greater percentage spread than the energy consumed by the pendulum instrument. The thickness index is probably satisfactory for following the uniformity of a given material. The energy consumed should, however, be a more reliable index for a Comparison of various rubber compounds or other materials. While a more or less definite dependencJ7exists between the elastic recovery and energy consumed by different samples of the same rubber, this relationship varies considerably when
VOL. 8, NO. 4
different rubber compounds or other substances are considered. This is illustrated by the data in Table 11, which shows the results of tests on various compounds and substances. The early stages of vulcanization are detected with the pendulum plastometer by the rapid change in the elastic recovery. I n many cases the elastic recovery will double before a noticeable difference is found in the energy consumed.
Literature Cited Behre, J., Kautschuk, 8, 2 (1932). DeVries. Arch. Rubbercultuur.. 8. . 223 (1925) Dillon, J. H., IKD. ENG.CHEM.,26, 345 (1934); Rubber Chem. Tach.. 7. 718 (19.74). _ _ . . , _ , . - ...~, Dillon, J. H., Physics, 7, 73 (1936). Dillon, J. H., and Johnston, N., Ibid., 4, 225 (1933); Rubber Chem. Tech., 7, 249 (1934). Hoekstra, J., Chem. Weekblad, 31, 745 (1934); Rubber Chem. Tech., 9, 55 (1936). f Hoekstra, J., Physics, 4, 285 (1935); Rubber Chem. Tech., 7, 136 (1934). Karrer, E., IND.EKG.CHEM.,Anal. Ed., 1, 158 (1929); Rubber Chem. Tech., 2, 601 (1929). Karrer, E., IND.ESG.CHEM.,Anal. Ed., 2 , 9 6 (1930). Lefeaditis, G. D., Trans. Inst. Rubberlnd., 9, 123 (1933). Marzetti, Ciorn. chim. ind. applicata, 6, 277, 567 (1924) ; India RubberJ., 66,417 (1923). Mooney, IND.ENG.CHEM.,-4nal. Ed., 6, 147 (1934); Rubber Chem. Tech., 7, 564 (1934). Peek, J.Rheol., 3, 345 (1932). Rossem, A. van, and Meyden, H. van der, Rubber Age (N. Y . ) , 23,438 (1928). Scott, J. R., Trans. Inst. Rubber Ind., 10, 481 (1935); Rubber Chem. Tech., 8, 587 (1935). Williams, I., IND.EKG.CHEM, 16, 362 (1924). ~
RECEWBD April 22, 1936. Presented before the Division of Rubber Chemistry at the 9lst Meeting of the American Chemical Society. Kansas City, Mo., April 13 to 17, 1936. Contribution No. 32 from the Jackson Laboratory, E. I. du Pont de Nemours & Company.
The Preparation of Naphthidine STUART COHEN AND RALPH E. OESPER, University of Cincinnati, Cincinnati, Ohio
S
TRAKA and Oesper ( 8 ) showed that naphthidine
(4,4'-bi-l-naphthylamine) is a satisfactory oxidationreduction indicator, particularly as an internal indicator in the volumetric determlnation of iron and chromium by means of dichromate. None of the methods hitherto available (1, 2,SJ6,7)for the preparation of naphthidine has been found satisfactory, for they are either laborious or yield only small specimens of this compound. A simple and practicable procedure has now been worked out, and the preparation of naphthidine in adequate quantities is here described. The starting materials are cheap, the time required is reasonable, and the yield of the finished product is good. The procedure may be divided into two stages: (1) the preparation of azonaphthalene, and (2) the reduction of the azonaphthalene to hydrasonaphthalene, which is not isolated but immediately rearranged t o naphthidine (Figure 1).
Preparation of Azonaphthalene The following modification of Lange's (5) method was found most suitable for the preparation of azonaphthalene: Thirty-five grams of a-naphthylamine hydrochloride are stirred into 500 cc. of water in an 800- to 1000-cc. beaker, 17.5 cc. of concentrated hydrochloric acid are added, the mechanical stir-
rer is started, and the solution is cooled in an ice bath to about 0'. Cold diluted sulfuric acid (21 cc., sp. gr. 1.84, plus 200 cc. of water) is then stirred in. The suspended amine salt is diazotized (by vigorous stirring, with customary precautions as to temperature) by slowly adding a cold solution of 14 grams of sodium nitrite dissolved in 80 t o 100 cc. of water. The reddish brown solution of the diazonium salt is allowed to stand 5 minutes (good cooling), and filtered at the pump, the filtrate being received in B precooled filter flask surrounded by an ice bath. The cold filtrate is transferred t o a 2-liter beaker (ice bath), the stirrer started, and a cold solution of 66 grams of anhydrous sodium acetate in 300 cc. of Tater slowly added, the temperature being kept between 0" and 5 . -4cooled solution of 31 grams of sodium sulfite in 200 cc. of water is then run in slowly, a vigorous evolution of nitrogen ensues, and 1,l'-azonaphthalene begins t o separate. After the addition of the sulfite solution has been completed, the stirring is continued for 5 minutes. The suspension is then taken out of the ice bath, and warmed on a water bath, and the tan or orange precipitate is filtered off, washed, and dried on a porous plate. The average yield of crude azonaphthalene, melting a t 180" to 184" C., is 31 grams (calculated 27.5). Pure azonaphthalenemelts a t 186" (S), 188" to 189" (4). The product obtained by the present procedure can be used for the preparation of naphthidine without further purification; in fact, the moist filter cake can be carried directly into the next step.
JULY 15, 1936
ANALYTICAL EDITION
0
"U
naphth id ine
/
dindphthylene
307
suspended solid has turned light tan. The heating is immediately discontinued, the suspension is cooled to room temperature, and 100 cc. of concentrated hydrochloric acid are added to precipitate the rest of the naphthidine hydrochloride. Under no condition must the solution be heated with the acid, since the dinaphthylene (1,l'-diamino-2,2'-dinaphthyl) present in the solution, when heated with hydrochloric acid, loses ammonia, forming dinaphthocarbazole, which precipitates with the naphthidine hydrochloride and greatly impedes its purification. The naphthidine hydrochloride is removed from the cooled suspension, sucked as dry as possible, suspended in 200 cc. of water, and 20 per cent sodium hydroxide solution is added in slight excess. The mixture is kept warm for 10 minutes at about 40" C., stirring frequently. The crude naphthidine is atered, washed with water until free of alkali, then sucked dry as possible. The crude base is boiled up with 120 cc. of ethanol, and pyridine (40 to 45 cc.) slowly run into the boiling suspension until the solid has dissolved. Any obvious impurities are removed by filtering the hot solution. The filtrate is allowed t o cool slowly, and the naphthidine separates in well-formed crystals, sufficiently pure for indicator purposes (m. p. 198-199'). Twenty grams of azonaphthalene produce 6 grams of purified naphthidine, corresponding to 33.5 per cent yield, calculated on the naphthylamine hydrochloride originally taken.
Literature Cited
l4dindbhtho edrbdzol
FIGURE1
Reduction of Azonaphthalene to Hydrazonaphthalene and Rearrangement into Naphthidine Twenty grams of crude azonaphthalene are suspended in 200 cc. of ethanol, and brought to a weak boil. A solution of 40 grams of stannous chloride in 100 cc. of concentrated hydrochloric a,cid is slowly run in (with occasional shaking) until the
(1) Clemo, Cockburn, and Spence, J. Chem. SOC.,1931, 1271. (2) Cumming and Howie, Ibid., 1932, 528. (3) Cumming and Steel, Ibid., 123,2464 (1923). (4) Hantzsch and Schmiedel, Ber., 30,81 (1897). (5) Lange, German Patent 78,225; Friedliinder, 4, 1016 (1897). (6) Nietski and Goll, Ber., 18,298, 3252 (1885). (7) Reverdin and la Harps, Chem.-Ztg., 16, 1687 (1892). (8) Straka and Oesper, IKD. ESG.CHEM.,Anal. Ed., 6, 465 (1934).
RECEIVEDMay 4, 1936
An Adiabatic Calorimeter WHITNEY WEINRICH
AND
HANNIBAL G.4SPAR1, Gulf Research and Development Corporation, Pittsburgh, Pa.
A sensitive adiabatic calorimeter is described in which the rate of oxygen absorption and the rate of temperature change due to the heat of reaction of finely divided substances with oxygen are measured. A differential thermopile and a photoelectric relay maintain adiabatic conditions; an electronic relay and an electrolysis cell make possible the automatic control of oxygen pressure. For certain samples of bituminous coal at one atmosphere pressure and at 50" C. initial temperature, oxygen absorption and temperature rise are nearly linear functions of time and one may be predicted from the other with considerable accuracy.
IT
WAS desired to measure simultaneously the rate of oxygen absorption and the rate of temperature change induced by the heat of reaction of finely divided substances with oxygen a t about 50" C. and at atmospheric pressure. To accomplish this purpose, a sensitive adiabatic calorimeter was constructed in which substantially no heat interchange between sample and environment was possible. Included in this apparatus were an automatic compensator t o maintain constant oxygen pressure and a nitrometer tube from, which
the volume of oxygen was read. Davis and Byrne (1) investigated the oxidation characteristics of various coals with an adiabatic calorimeter. In their apparatus the temperature of the calorimeter liquid was made by electrical means to follow closely the temperature of the coal. Kohman (3) studied the effect of oxygen absorption on the aging of rubber. For maintaining constant oxygen pressure over the sample, his apparatus employed an automatic compensator. Specifically, a manometer was so constructed that any decrease in pressure due to an absorption of oxygen caused a mercuryplatinum contact to close and permitted an electric current to flow through a solution of oxalic acid. The gases liberated by electrolysis forced mercury into a nitrometer tube and thus decreased the volumetric capacity of the system and restored the original pressure. The volume of oxygen was then read directly from the nitrometer tube. The calorimeter described here is a combination, with some modifications, of the above two types of apparatus. To ensure an even temperature, the entire reaction unit, which is % closed system, is immersed in the calorimeter bath. Heat of reaction is measured as a function of the temperature of t h e bath, and the oxygen absorption is read from the nitrometer tube. The adiabatic control and the control of oxygen pressure are automatic.
Control of Adiabatic Conditions The adiabatic calorimeter is a modified de Khotinsky aquariumtype thermostat bath of about 300 liters (79 gallons) capacity. Figure 1 shows an assembly sketch of the complete a paratus. A turbine-type stirrer efficiently agitates the water of ttis bath, and an external spill-over device serves to supply continuously
