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INDUSTRIAL AND ENGINEERING CHEMISTRY
The experiments described above indicate that P-phenylanthraquinone is the principal product resulting from the removal of water from 4'-phenyl-2-benzoyl benzoic acid. When the chlorophenylanthraquinones were oxidized according to the procedure previously described, the resultant products melted a t 290" C. (cor.). Tests for chlorine gave negative results. The ethyl esters melted a t 147" C., indicating that the product of oxidation was anthraquinone-bcarboxylic acid. Since the chlorine is removed upon oxidation of the halogen derivatives, the phenylanthraquinones must contain the substituent in the phenyl nucleus. Since the relative position of the halogen to the phenyl linkage remains unaltered by ring closure, these products must be principally 4'-chloro- and 2'-chloro-P-phenylanthraquinones.
Vol. 22, No. 6
The amino compounds derived from the chloro-p-phenylanthraquinones will doubtless have an analogous structure. Acknowledgment
The author wishes to acknowledge the assistance of H. P. Newton of this laboratory, who carried out the combustion analyses and helped generally in the preparation of some of the materials. Literature Cited (1) Elbs, J. Drakf. Chem., 41, 145 (1890). (2) Kaiser, A n n . , aST, 95 (1890). (3) Liebermann and Glock, Ber., 17, 890 (1884). (4) Scholl and Novius, I b i d . , 44, 1075 (1911). (5) Turner and LeFevre, J. Chem. Sac., 1928, 245
Heat of Combustion of Carbon' Wm. B. Plummer COMBUSTION UTILITIESCORPORATION, LINDEN,N . J.
By degassing various types of carbons in vacuum at tubing, B. Connection to URING the course of 1000' C. and maintaining the samples in vacuum the vacuum pump, gage, etc., various studies on the throughout the cooling and weighing operations, heats was made a t the top of the physical properties of of combustion appreciably higher than any previously bulb. The s a m p l e s were c a r b o n b l a c k s a n d other reported in the literature are obtained. The value e v a c u a t e d for 2 hours a t forms of carbon it was desired found for an amorphous carbon is 8272 calories per 1000" C. to about 1 mm. to investigate the possible gram, while a pure graphite gave 7932 calories per gram, final pressure. After cooling, correlation between heat of which are, respectively, 1.5 and 0.9 per cent higher than the extra heavy screw clamp, combustion and certain previous values. C, was closed tightly, the other properties. Numerous These results are of a preliminary character, but intube inverted, a suitable determinations were therefore dicate the desirability of confirmatory and extended amount of carbon shaken made on various materials on studies using similar methods and precautions, since into bulb A , and screw clamp an oven-dry basis and also the heat of combustion of graphite is one of the most E closed off. T h e b u l b after degassing in vacuum Ras then removed and set important data of thermochemistry. a t 1000" C. I n the latter up its shown in Figure 1, a case t h e m a t e r i a l was exsample tube, D,fitted tightly onto rubber stopper F, and the posed to the air only for a moment during its introduction into sample bottles, which were then reevacuated, and for a system evacuated. By tapping and manipulation of clamp few minutes prior to weighing the samples for the bomb com- E the desired amount of sample could be shaken into tube D, bustion. Certain apparent discrepancies in results led, how- which consisted of a previously cleaned 1 x 10 cm. Pyrex ever, to modification of this procedure, such that the ma- test tube drawn down to a 1-2 mm. constriction, and weighed. terials were not exposed to air until after the samples for The tube was then sealed off without sepmation of the upper the bomb combustion had been weighed out and just prior and lower halves, cleaned again, dried, and weighed. The to their introduction into the bomb. This modified proce- heat of combustion was determined in a standard oxygendure, by elimination of all possibility of gas adsorption prior bomb calorimeter, frequently checked against standard bento weighing, has resulted in heats of combustion 1 to 2 per zoic acid. All results cited represent the average of two cent higher than corresponding values previously reported determinations in satisfactory agreement with each other. It will be obvious that this method of weighing introduces in the literature. a buoyancy effect in the case of samples weighed in yacuum. Samples Used The average volume of the sealed portion of the weighing The graphite used was a special material furnished by the tubes was 2.7 cc., while the volume of 1.0-gram carbon sample Acheson Graphite Company containing only about 0.05 may be taken as 0.5 cc. Hence to bring all results onto the per cent ash, while the carbon blacks were standard grades usual weight-in-air basis, taking the density of air as 0.0012 as furnished for use in the rubber industry and contain not gram per CC., the weights of the vacuum-weighed samples should be corrected by adding 0.0012 X (2.7 - 0.5) = 0.0026 over 0.03 per cent ash. gram. In other words, for a 1.00-gram sample a negative Method correction of 0.26 per cent should be applied to the observed heating value to bring it to a weight-in-air basis. This has The degassing operation was carried out in a closed-end been done in the data shown herein. silica tube about 3.5 cm. inside diameter and 60 cm. long Results located vertically with its lower end in the central (constanttemperature distribution) zone of a suitable electric tube furA large number of determinations of this type were made nace, about 20 grams of carbon material being taken. The in the course of this work, but only certain salient data of upper end of the tube was closed by a one-hole rubber stop- general importance will be reported here. Table I shows the per to which bulb A , Figure 1, was attached by heavy rubber comparison between the three methods of preparation of the sample and tabulates previously accepted values. 1 Received March 11, 1930.
D
INDUSTRIAL AND ENGINEERISG CHEMISTRY
June, 1930
The agreement of the oven-dry graphite figure with the previous literature values is a reasonably close check on materials and technic. The results of the degassed and vacuumweighed materials show a greater difference from those on an oven-dry basis the greater the adsorptive capacity of bhe carbon, but even for graphite the difference is many times the probable error. The value of 8272 calories per gram observed for degassed and vacuum-weighed carbon black is, as far as known, the highest observed for any form of carbon, being 1.52 per cent higher than Roth's value for amorphous carbon. Such carbon black may be regarded as probably one of the most "primary" forms of carbon (except that which may be formed at low temperatures by catalytic decomposition of carbon monoxide), since the temperature of the iron channels on which it is deposited is not appreciably over 550" C. On the other hand, Roth and Doepke((i), have found that electrode carbon heated a t 1000" C. (period of heating not stated) already shows some decrease in heat' of combustion, indicating incipient graphitization. Furthermore, in the present work a sample of standard channel carbon black given a 0.5-hour heat a t 2000" C. in an inert atmosphere and then degassed a t 1000° C. in vacuum and weighed in air showed a heat of combustion of 8094 calories per gram compared with 8181 calories per gram for the same material without the high-temperature heating. These facts indicate that while, as previously stated, the observed values for amorphous carbons are higher than any before reported, it is probable that they still do not represent the highest attainable by the present method. Unfortunately, however, time has not been available for any detailed study of the effect of temperature and time of degassing on the final heat of combustion. of C o m b u s t i o n of Carbon Methods OVENDRIED SAMPLE AT 110' C. Calories,/ gram
Table I-Heats
Prepared by Various DEGASSED AT 1000° C. Weighed Weighed in air in vacuum" Calories/ Calories/ gram gram
VALUES AS DETERMINED
Standard channel carbon black Compressed channel carbon black Graphite, Acheson No. 2301
7812 7939 7875
8181 8221
..
8272 7932
VALTES FROM LITERATCRE
Graphite (International Critical Tables) Graphite (6) Amorphous carbon (6) Corrected to weight-in-air basis.
7867 7866 8148
..
..
, .
..
Effect of Oxidation
Certain experiments have also been carried out on the effect of oxidation of blacks on their heat of combustion. The oxidation was carried out by spreading the black in a thin layer on a light oxidation-resistant alloy trough and introducing it into an inclined open-end tube furnace held a t 650" C., the black being raked over a t frequent intervals. Owing to evolved heat the black doubtless rose to local temperatures iii excess of 650" C. The data of Table I1 are for a sample oxidized for such a length of time as t o give 20 per cent consumed. of Oxidation of Blacks on Heat of Combustion DEGASSED OVENAT 1000' c. DRIED n'.eighed SAMPLE A T 110' e. in air Calorieslgram Calories/gram Standard channel carbon black 7812 8181 Compressed channel carbon black 7939 8221 Standard channel black, oxidized 7726 8217 Standard roller-process black 7309 8211
T a b l e 11-Effect
It will be seen that, although the black was heated to a t least 700' C., which from other data herein should tend to increase its heat of combustion by removal of impurities,
63 1
actually the heating value was decreased. This shows clearly that oxygen, or its reaction products, is adsorbed a t temperatures above 650" C., although Johnson (3) has expressed the view that oxygen is adsorbed by carbon blacks below 450-500O C. and desorbed a t higher temperatures. Another interesting point to be noted from Table I1 is that channel carbon black, oxidized or not, and roller-process black, which has a high oxygen content as produced commercially, show the same heat of combustion under comparable conditions after degassing in vacuum a t 1000" C. Discussion
-F
mw"m Probably the most important point brought Out by the present work is the a p parent fact that the accepted value for the heat of combustion of graphite is about 1 per cent low. Since this is one of the most basic and important data of thermochemistry, it is to be hoped that w o r k o n t h i s point, using methods and p r e c a u t i o n s analogous to these used here, may be continued and am- To W = W ~ plified by other investigators. The present work should also be extended by parallel determinations of total carbon content. This was attempted here, but satisfactorily concordant results could not be o b t a i n e d within the time available. It may, nevertheFigure 1 less, be noted that all tests m a d e on degassed carbons weighed in vacuum showed slightly less than 100 per cent carbon by the usual combustion methods, after correcting the observed weight to a weight-in-air basis by adding the proper correction for the buoyancy of the evacuated weighing bulb. In view of the incompleteness of the present data, conclusions on this point have been drawn since according to the character of such residual non-carbon elements or material the heat of combustion might be either raised or lowered by its complete removal. In any discussion of the basic properties of carbons, the old question as to the existence of amorphous carbon as a separate modification must always arise. Debye and Scherrer (2) and Asahara ( I ) , on the basis of x-ray photographs, postulate the transition from amorphous carbon to graphite as merely a matter of increasing unit crystal size. Chaney (d), on the other hand, postulates two separate forms of amorphous carbon, yielding two distinct modifications of graphite on heating. Roth and Doepke (6) find a difference of 292 calories per gram between graphite and their most primary amorphous carbon, and from Laue x-ray photographs calculate a unit crystal size of lo-' cm. In order to account for the 292 calories per gram difference on a basis of unit crystal size and total surface energy, a surface tension of 400 ergs per sq. cm. becomes necessary, which they consider improbable and hence assume the existence of amorphous carbon as a distinct modification. The present work extends this difference to 340 calories per gram and might be taken to confirm the latter view. The theory that seems most in accord with the general properties and behavior of so-called amorphous carbons is that they are not modifications of elemental carbon (plus
INDUSTRIAL ,4ND ENGINEERING CHEMISTRY
632
certain adsorbed or contained impurities), but very high molecular, highly unsaturated hydrocarbons; in other words, they are carbon complexes in which the fields of force between the carbon atoms are unbalanced by an occasional stray hydrogen atom, thus preventing the stable crystallization of the carbon atoms and producing a general state of unsaturation and hence of surface activity. Graphite is thus to be regarded as the only stable crystal form of carbon other than diamond, but amorphous carbon is not to be considered as a physical modification of graphite. This general view is who has found that all favored by the results of Lowry (i), oxygen is evolved from charcoals below 1000° C., but that the hydrogen content is still 0.48 per cent, decreasing to about 0.1 per cent at 1300" C., while his coefficient of surface activity (cc. COz adsorbed per cm. mm. total pore volume) did not decrease appreciably until above 1000" C. I n view of the high heat of combustion of hydrogen per gram, and the degree of carbon unsaturation which could reasonably be produced by 0.5 to 1.0 per cent hydrogen ( I hydrogen atom per 16 to 18 carbon atoms), it seems quite possible that this can account for the 341 calories per gram increased heat of combustion observed as compared with that for graphite.
Vol. 22, No. 6
On this basis the x-ray observations of Debye and Scherrer (Z), which they thought indicated that amorphous carbon consists of agglomerates of extremely small true crystals of
graphite, would rather be interpreted as showing the local formation of such crystals or minute regions of stable arrangement of carbon atoms at points where the hydrogen atoms have become too few and too widely separated to prevent this crystallization. That this hydrogen is very firmly held is shown, not only by the temperature observed by Lowry that was required to remove it, and by the temperatures found necessary to produce appreciable graphitization (Roth and Doepke, ci), but also by the data of Table 11. Evidently preliminary oxidation, either during or after manufacture, has no effect on the internal composition or structure as reflected by the heat of combustion after degassing in yacuum a t 1000" C. Literature Cited (1) Asahara, Japan J . C h e m . , 1, 35 (1922). (2) Debye and Scherrer, Physik. Z . , IS,291,(1917). (3) Johnson, IND.E N G .CHEM.,21, 1288 (1929). (4) Lamb, Wilson, and Chaney, J. I R D .E R G .CHEW.,11, 420 (1919). (5) Lowry, J . Phys. Ckem., 34, 63 (1930); J . .am.Citem. Soc., 46, 824 (1924). (6) Roth and Doepke, B e y . , 60, 530 (1927).
Chemical Character of the Hot Springs of Arkansas and Virginia" Margaret D. Foster UNITED STATESGEOLOGICAL SURVEY, WASHINGTON, D. C.
N COSNECTION with studies of the hot springs of Arkansas, made at the request of the Sational Park Service, analyses of samples from several of the springs, taken at different times in the year, were made in the waterresources laboratory of the United States Geological Survey.
I
1 Received April 3, 1930. Presented before the Division of Water, Sewage, and Sanitation Chemistry at the 79th Meeting of the American Chemical Society, Atlanta, Ga , April 7 to 11, 1930 2 Published by permission of the Director, United States Geological Survey.
Some of these analyses are given in the accompaiiying table, together with analyses made by J. K. Haywood ( S ) , of the Bureau of Chemistry of the United States Department of Agriculture, in 1901. Similar analyses of samples from Warm Spring Valley, Va., were made by the United States Geological Survey in connection with a cooperative investigation initiated by the Virginia Geological Survey. Some of these analyses are given in the table, with one analysis from a series made by F. W. Clarke (I), of the United States Geological Surrey, in 1884. The table also includes analyses
tE
2
29
19
30
23
24
Analyses of Hot Springs and Public S u p p l i e s (Numbers refer to analyses in table)
21
22
27
