Oct.,
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
1920
by heating sugar, and which, to the eye, exactly matched the lime-glucose solution. Some of the carbons, moreover, take up the dull grayish color from cane juice which bone-black fails to absorb, and their use is being urged for making refined sugar directly from cane juice. SELFCTIVE DECOLORIZING ACTION OP DIFFERENT AGENTS Complete color removal is proportionally much more difficult than partial removal. For instance, a certain percentage of decolorizing carbon added to a raw sugar solution removed 50 per cent of the color, a similar percentage added to the filtrate removed only 2 5 per cent of original color, and a third treatment removed but 7 per cent. This suggests that in the complex of coloring substances present in a raw sugar there may be some which are more easily removed than others. Some further knowledge of this phase of the subject may be attainable through investigation of the effects of decolorizing agents on colors of different wave lengths. With this in view, a series of readings were made with the Hess-Ives tintometer on some specially prepared solutions, both before and after subjecting them to the absorbing action of two different decolorizing substances. The scale on the instrument was replaced by one devised by the writer to g i k e a more exact index of the amount of light passing through the observed solutions. Having found that any particular amount of color solution gave a reading on the reversed scale of ten times the square root of the amount of color, the new rscale was constructed with I coinciding with the original I O (of the reversed scale) with 4 lying on 20, with 9 on 30, with 16 on 40. with 2 5 on 50, and so on, up to IOO on 100. Csing this scale, the. following results were obtained, expressed in terms of color tra.ismitted, for IOO readings. 100 Cc. Treated with------15 G Bone-Black- 0 5 G CarbonRed Green Blue Red Green Blue 25 97 78 25 97 78 96 88 62 99 95 80.5 c
IVIATERI 41. Caramel Original . . . . . . . . Treated . . . . . . . . Lime-Glucose Original . . . . . . . . Treated , , . , . ,
.
97 99.7
85 99.6
50 97.2
97 99.6
85 99.2
50 94
It is rhus apparent that different colored substances require different decolorizing agents to yield the best results. It would seem, also, that successive treatments with different decolorizers might give greatly augmented decolorization, but thus far results have bee:i disappointing. This field merits full investigation. I n refining, it is desirable to use about I O O Ibs. of bone-black t o 100 lbs. of raw sugar. This will remove about 25 to 35 per cent of the ash, about 35 to 45 per cent of the organic impurities, and about 7 j per cent of the color. This involves several filtrations, and as the ash amounts to about 0.6 per cent of the raw sugar and the organic matter t o about twice as much, while the weight of the coloring matter is but slight, the absolute amount of these substances taken up is always quite small. The decolorizing carbons in some cases succeed in removing as much C Q ~ as J ~2 0 times their weight of bone-black will remove. The ash absorption is frequently not so good as in char work, slight as that is. Bone-black is used in filters 20 ft. deep, so that the liquor passing down comes successively into contact with numerous layers of fresh char, thus giving up all its color and producing for long periods a colorless filtrate, while a decolorizing carbon in powder added directly to colored liquor in a tank a t once absorbs what color it can, and when this homogeneous mass is filter-pressed all the effluent is alike. For white sugar making, this is not so advantageous as the char method, and so we find a multiple decolorization and filtration coming into vogue. -%gain, the wearing down of decolorizing carbon in use tends to give slow filtration, and, as it is not convenient to screen out the finer particles, a most ingenious contrivance has been developed b? the General Norit Company to scrape off the accumulated deposit from the filter leaves continually, so that the filtration may continue in t h e most unobstructed manner.
IO17
Revivification can be carried on by chemical means in the case of carbons much more easily and safely than in the case of boneblack, and this field presents interesting undeveloped possibilities. Decolorizing carbons of fine properties have been made from quite a number of waste materials and some very cheaply. The desideratum is one cheap enough to throw away after using once, and which will absorb ten to twenty times as much color as boneblack, and ash and organic impurities in proportion. This may not come, but the advance has been so rapid we may not unreasonably expect to see some approach to it in the not distant future. RECENT WORK ON DECOLORIZING CARBONS The subject of decolorizing carbons is a large field in itself, and although much very good work has been published on it of late it can only be touched upon here. Chaney has shown’ that all primary amorphous carbon consists essentially of a stabilized complex of hydrocarbons absorbed on a base of active carbon. These primary carbons as such do not possess a high specific absorptive power, the active carbon having been saturated by the hydrocarbon absorbed by it. The process of activation must, therefore, consist fundamentally in the separation and removal of the hydrocarbons lrom the active carbon. This active modification of carbon is formed whenever carbon is deposited a t relatively low temperatures by chemical or thermal decomposition of carbon-bearing materials; in general, below 500’ to 600’ C. Zerban has published in recent bulletins of the Louisiana Experiment Station most interesting results in regard t o the preparation and properties of these carbons. Bradley2 has recently published an excellent resum6 of his results in the study of the properties of Norit. These and other pioneers have shown the way in beginning to develop this method of preparing and using decolorizing carbons. It remains for the subject to be followed up industriously to attaiii results that will amply repay all efforts in the investigations of these fascinating questions. HISTORY OF THE PREPARATION AND PROPERTIES O F PURE PHTHALIC ANHYDRIDE By H. D. Gibbs E. I .
DU P O N T DE
NEMOURS 82 CO., WILMINGTON, DELAWARP; Received July 1, 1920
A Cnited States patent3 recently granted, which claims as an article of manufacture “phthalic anhydride substantially chemically pure and having a melting point above 130’ C., corrected” and “phthalic anhydride in the form of colorless, needle-like crystals substantially chemically pure and having a melting point above 130’ C., corrected,” raises the question of the history of the preparation and properties of pure phthalic anhydride, particularly of the melting point. As will be shown later in this article, phthalic anhydride of a degree of purity which undoubtedly exceeds that of the product described in this patent was prepared and described a t least as early as 1902 by Van de Stadt,4 and in 1919 (prior to the date of filing of the Chem. News, 119 (1919), 283. J . Sac. Chem. I n d . , S 8 (1919), 396. 3 U. S. Patent 1,336,182, Phthalic Anhydride, issued April 6, 1920, t o C. A. Andrews, assignor t o the Se1d.n Company of Pittsburgh, P a , (Application filed October 14, 1919.) 4 “Bernsteinsaiire und Phthalsaiire-anhydrid in ihrem Verhalten gegeuuber Wasser,” Z . physik. Chem., 41 (1920), 353. Van de Stadt’s excellent investigation carried out in Amsterdam in collaboration with Prof. Bakhuis Roozeboom has not received the attention which it deserves, since it has been overlooked by compilers of the standard organic treatises, such as Beilstein’s “Organische Chemie,” Richter’s “Organic Chemistry,” and Meyer and Jacobson’s “Lehrbuch der Organischen Chemie,” and also by the compilers of Zandolt-Bornstein’s “Physikalisch-Chemische Tabellen.” It is, however, noted in a recent American treatise, Seidell’s “Solubilities of Inorganic and Organic Compounds,” 2nd E d . , D. Van h’ostrand Co , Xew York. 1919, p. 491. 1 2
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application for U. S. Patent 1,336,182) by Monroe.’ A process by pressing between filter paper after removal of acetyl chlorick of manufacture by air oxidation (using vanadium and molybdeby absolute alcohol. num oxides as catalysts) which yields a product in the form of Lachowiczl prepared phthalic anhydride by warming phthalyl “long, colorless, glistening needles,’I2 substantially chemically chloride with lead nitrate; the crude substance was purified pure and having a melting point above 130’ C. (corrected), by recrystallization from benzene. The melting point found has been described and patented by the author and C. C ~ n o v e r . ~(128’C.) agrees with the previous values of Lossen and Anschuta, It was early observed in the development of the air-oxidation although the method of purification is scarcely sufficient to process that the product melted above 130’ C., and the author eIiminate all impurities. Stohmann2 prepared phthalic anhydride by distillation of stated in a n article published in THIS JOURNAL in 1919:4 “ I t is interesting to note that phthalic anhydride produced by this commercial phthalic acid, and recrystallized the crude sublimate process is of a remarkable degree of purity. Naturally, it is from benzene-ligroin mixture. The observed melting point (128’ C.)is in agreement with that found by the previous infree from chlorine or sulfur compounds, common impurities in phthalic anhydride as formerly found on the market.” Mon- vestigators, but this work is open to the same criticism, the roe’s investigation was, indeed, carried out a t my suggestion phthalic acid prepared by chromic or permanganic oxidation of while we both were employed in the Color Laboratory of the naphthalene in sulfuric acid solution (with mercury sometimes present as a catalyst in large-scale operations) is well known Bureau of Chemistry, in view of the confusion which existed frequently to contain sulfur and chlorine compoundsJ which in the earlier literature and in the standard organic treatises in regard to the melting point of pure phthalic anhydride, are not readily removed by sublimation or recrystallization. Indeed the first recorded investigation in which sufficient and in the absence of knowledge concerning Van de Stadt’s precautions were observed to insure a chemically pure anhydride, earlier investigation, to which Doctor Monroe has called my and in which the observations were recorded to have been taken, attention since the publication of his own article. I n view of these facts, the fallacy of the claims of Andrews not in the capillary tube manner, but with thermometer immersed in the melt, is that of Van de Stadt,4 who states? “I to pure phthalic anhydride as a n article of manufacture is very apparent. It is difficult to conceive the grounds upon which determined the melting point (of phthalic anhydride purified by distillation) in a sealed tube with sealed-in thermometer, such a patent could have been granted. I n order that the matter since the substance absorbs water readily, and in this manner may be clarified, the following summary of chemical literature obtained the value 131.2’ C.” Van de Stadt examined the bearing on these topics is presented: Phthalic anhydride was discovered a t least as early as 1836 melting points of various mixtures of anhydride and water, and also determined the eutectic temperature of phthalic anby Laurent,6 who prepared the acid by oxidation of naphthalene hydride and acid to be 129.6’. He describes the experimental with chromic acid, and obtained phthalic anhydride by sublimaprocedure in some detail: tion of the acid. The melting point of the sublimedproduct A mixture of 95 molecular per cent anhydride and 5 molecurecorded by this observer is IO^', concerning which Lossen6 lar per cent water was heated in a small open tube ahd the states? point of a final solidification observed. I n spite of constant stirring, a large portion of the mass remained liquid after copious 105’’ Reaumur corresponds to 13 I Celsius (Centigrade). It appears, therefore, that Laurent carried out his observation crystallization had occurred until the temperature of 129.8’ with anhydride which contained some acid, and used a Reaumur was reached, when a second crystallization occurred, during thermometer.. . I found the melting point of anhydride which the thermoyeter remained constant * 8 minutes between 129.8’ and 129.6 Another mixture of 90 molecular per cent whizh was prepared by one sublimation of phthalic acid to be anhydride with I O molecular per cent water also gave such a 131 C.. . , . . , The large discrepancy between this and the (eutectic) point a t rz9.7’, and the same phenomenon was obvalue given by Laurent ( 1 0 5 ’) led me to repeat the determination. I used for these experiments phthalic acid prepared in various served very markedly with a mixture containing 70 and 30 ways, which had been completely transferred into the anhydride molecular per cent. by long-continued heating to the boiling point (of the anhydride) We see, therefore, that two distinctly different crystal forms . . . . . . . . A large number of very careful determinations gave appear (first acid and then anhydride). The first crystals may consistently 128’ C. as the melting point. be agitated with the mother liquor without further crystallization occurring; they are, therefore, phthalic acid, which had been Although conclusions of little value from the viewpoint of dissolved in the molten anhydride. Microscopic examination exact thermometry may be drawn, one may not altogether led to the same conclusion. exclude the possibility that pure phthalic anhydride of subIt is to be noted that the eutectic obtained by the very careful stantially correct melting point (compare Van de Stadt and work of Monroe for the system phthalic anhydride-phthalic Monroe, Loc. cit.) was thus obtained even a t this early date by acid exactly checks the work of Van de Stadt, and the latter its discoverer, and in one instance by Lossen. article was not discovered by Monroe until after the publicaAnschiitzs prepared phthalic anhydride by the dehydration tion of his own work. of phthalic acid with acetyl chloride, and found its melting point I n view of the above statements of facts, i t is evident that the t o be 127’ C. No exact conclusions in regard to the melting purest phthalic anhydride is not a new product. point of pure anhydride may be drawn from this observation, however, since the crystals of anhydride were purified merely NEW FIELDS OF PHYTOCHEMICAL RESEARCH OPERED U P BY THE CULTIVATION OF MEDICINAL PLANTS lTx1s JOURNAL, 11 (1919), 1116. (Read before t h e Dye Section, 58th Meeting of the American Chemical Society, Philadelphia, P a . , S e p ON AN ECONOMIC SCALE6 tember 2 t o 6, 1919.) By Edward Kremers 2 Monroe, LOG. cit.
. ...
a U. S . Patent 1,284,888. Process for the Manufacture of Phthalic Anhydride, Phthalic Acid, Benzoic Acid and Naphthoquinones, issued Nov. 12, 1918, t o H. D. Gibbs and C. Conover (application filed May 12, 1917); U. S. Patent 1,285,117. Process for the Manufacture of Phthalic Anhydride, Phthalic Acid, Benzoic Acid and Naphthoquinones, issued November 19, 1918, t o H. D. Gibbs and C. Conover (application filed February 17, 1917). 4 “Fhthalic Anhydridc. I-Introduction,” THISJOURNAL, 11 (1919), 1034 (Received Aug. 19, 1919). 6 Rev. Scient., 14, 5 6 0 ; Compt. rend,, 81, 3 6 ; A n n , 19 (1836), 38. 6 Ann., 144 (1867), 76. 7 Translated from the original German. 6 Ber. 10 (1877). 3 2 6 .
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UNIVZRSITY OF
WISCONSIN,
MADISON, WISCONSXN
The milling of half a n acre of belladonna plants or the a s tillation of an acre of peppermint, when carried out by an ohBer., 17 (1884) 1283. J . p ~ ~ hChem., t . 40 (1889), 139. a Gibbs, LOGcit. 4 LOG.‘it.; sea also an earlier investigation by this aiithor, Z . Blaysik Chem., 81 (1899), 250; Bancroft, J . Phys. Chem , 1899, 93; R a t n a y and Young, Trans. Roy. SOC.London, 117, I 103. 5 Translated from the original German. 6 Presented a t the 58th Meeting of the American Chemical .%ciety, Philadelphia, Pa., September 2 t o 6, 1919.
