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T H E J O U R N A L O F I N D U S T R I A L A N D E N G 1 4 V E E R I N G C H E M I S T R Y Vol.
12,
No. io
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 molybde- by 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 an article published in THIS JOURNAL in 1919:4 “It 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 Bureau of Chemistry, in view of the confusion which existed present as a catalyst in large-scale operations) is well known frequently to contain sulfur and chlorine compoundsJ which in the earlier literature and in the standard organic treatises are not readily removed by sublimation or recrystallization. in regard to the melting point of pure phthalic anhydride, Indeed the first recorded investigation in which sufficient and in the absence of knowledge concerning Van de Stadt’s earlier investigation, to which Doctor Monroe has called my precautions were observed to insure a chemically pure anhydride, and in which the observations were recorded to have been taken, attention since the publication of his own article. In view of these facts, the fallacy of the claims of Andrews not in the capillary tube manner, but with thermometer imto pure phthalic anhydride as a n article of manufacture is very mersed in the melt, is that of Van de Stadt,4 who states? “I 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. In order that the matter may be clarified, the following summary of chemical literature since the substance absorbs water readily, and in this manner 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 with chromic acid, and obtained phthalic anhydride by sublima- hydride and acid to be 129.6’. He describes the experimental tion of the acid. The melting point of the sublimedproduct procedure in some detail: 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. In spite of constant 105’’ Reaumur corresponds to 13 I Celsius (Centigrade). stirring, a large portion of the mass remained liquid after copious 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 131 C.. . , . . , The large discrepancy between this and the anhydride with I O molecular per cent water also gave such a (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 In 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 the Dye Section, 58th Meeting of the American Chemical Society, Philadelphia, Pa., 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, to 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, to 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 .
.
UNIVZRSITY OF
WISCONSIN,
MADISON, WISCONSXN
The milling of half an 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.
Oct., 1920
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
serving scientist, ought to be productive of results, new in more ways than one. To the scientist who has conducted his experiments on a relatively small laboratory scale, the problems which confront him in milling or distillation may result in solutions new to him although old to the technologist. The fact, however, that the technologist does not record his experiences for the benefit of the scientist may make the observations of value t o others if recorded. It is not to fields, new in this sense, that the writer wishes to draw your attention. The cultivation of medicinal plants on a semi-economic scale and the working up of the harvest, whether fresh or cured, present to the observing scientist fields that are new in quite a different sense. To some of these, selected a t random, and the lessons already learned from them, the writer desires to invite your attention.
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occurred when the coarse powders had been incinerated. A microscopical examination of the fine powder revealed that it consisted not only of soil particles, but also of innumerable leaf hairs. Hence, aside from the lessons already learned from the milling experience with digitalis, we have several additional lessons to record. The first of these is that in the milling of drugs we may have a very convenient means of separation of plant organs for special investigation, chemical or otherwise. Second, Dr. Richtmnnn has been of the opinion, based on field observations, that the attraction of the plant for the potato beetle-this season all of the second year crop had to be harvested early in May because the potato beetle, finding no potato vines, threatened to devour every leaf-is due to a peculiar odor of the leaf. What more natural, therefore, than to infer that these DIGITALIS leaf hairs are the reservoirs in which are stored the possible A t the meeting of the SOCIETY held a t Urbana in April 1916, aldehydes, which on being heated in the crucible caused the the writer presented to the Division of Pharmaceutical Chem- irritation of the throat. Already a preliminary distillation with istry specimens of digitalis that had been milled and sifted with water vapor of the fine powder, rich in hairs, as well as a set of analytical sieves. Whereas the No. 20 powder prepared soil particles, has been made. It is expected that after the 1919 for an eastern hospital contained I O per cent of ash, the No. 100 crop has been milled a sufficient amount of this fine powder will Powder had an apparent content of nearly 80 Per cent. The have been separated t o make possible a careful study of this apparent ash content of the intermediate powders varied corre- problem. spondingly according to the degree of fineness. This observaLast and possibly not least, if the odoriferous substances of the’ tion afforded a ready explanation of the greatly varying records hyoscyamus that attract the beetles can be identified, it may be of ash content of digitalis as found in literature.’ Since that possible to attract the beetles t o traps containing these subtime a microscopica~study of leaves with hairy surfaces and of stances and to save the crop for further growth. the soil adhering to such leaves has been made by Tschirch. PEPPERMINT The first lesson to be learned from this experience was a The cultivation of an acre of peppermint during the Season simple mechanical method of purifying digitalis and other leaves of 1 9 1 7 enabled the Station to initiate a series of experiments’ (hyoscyamus, sage, This method has already been in distillation. Mr. Norbert Mueller, the government expert, adopted by others. distilled the fresh peppermint harvested late in the summer of A second lesson is one for the analytical and The Wisconsin pharmaceutical Experiment Station that season and Professor E. R. Miller, a t the time chemist certainly had no commercial motives when it gave of its of the Station, cohobated the aqueous distillate which had been digitalis to eastern hospitals, yet, with all the care exercised in saved for that purpose. Suffice it here to calf attention to the points: cultivation and curing, a so-called crude drug had been proFirst, the additional oil obtained by cohobation amounted duced that yielded about 25 per cent of apparent ash. A high ash emtent-and ash standards have again into greater to about I O per cent of the oil obtained by the first separation. This oil differs materially, quantitatively if not qualitatively, prominence-does not necessarily indicate adtllteration, not from the regular crude, i. e., non-rectified peppermint oil, and even carelessness. It may be largely a matter of the character study* of the soil on which the foxglove has been raised, or a question hence invites Second, for every liter of oil separated a liter of waterof rains, quite beyond the control of the grower. soluble constituents was obtained by repeated cohobation, A third lesson is revealed in the possibility of controlling the or, to put it in other words: For a thousand-acre peppermint process of milling so as to yield the largest percentage of powder, provided, naturally, that such is the object of the miller. farm we have been throwing away from One to two thou’and A fourth problem was suggested a t the Urbana meeting by the liters Of Organic Third, whether or not these observations prove of economic late Mr. Wllbe&, who pointed out that if the apparent ash conimportance, their biochemical significanceis in no way diminished. sists largely of clay, the occluding effect of this admixture may Just as the commercial d w miller has kepi his experiences be such to interfere with the therapeutic effect of the active constituents. The solution of the problem will be a joint one largely to himself, so the distiller of peppermint and other aromatic herbs has not infrequently kept his observations to for pharmacist and pharmacologist. himself. For the most part he has not found the time in the stilla,lother problem is met in working up the by-products of the for pharmaceutical preparations of desired rush of the season to interrupt his commercial production and t o qtrength or, better still, of definite chemical compos~t~on~ These indulge in experiment. At times also he has not been in a posiproblems have been attacked and it is hoped may form the sub- tion to interpret properly such observations as he has made. The distillation of plants and parts of plants in the production jects for separate reports. of volatile oils has proven one of the most satisfactory methods HYOSCYAMUS of isolation in phytochemistry. Yet in comparatively few instances have the less striking water-soluble volatile constituents the milling experience worked out in connection with received any attention whatever. digitalis was applied to hyoscyamus by our pharmacognosist, Dr. The experiment with peppermint could not be repeated in W. 0. Richtmann, and his assistant, Mr. F. Bacon, a striking 1918 because of the winter-kil!ing Of the mint. During the observation was recorded. The ash determination happened present season, however, the aqueous distillate is again being to be made in the open laboratory rather than in the hood. coilected for cohobation. During the season of 1 9 1 7 Professor the assay of the fine powder there resulted a smoke which caused 1Miller collected the aqueous products of a number of distillations, the occupants of the room to cough. No such result had and his results are soon t o be published as a Station circular 2 1 A compilation of ash determinations of vegetable drugs has been prepared by several students, but the voluminous manuscript has n o t yet been edited for publication
1 2
Wisconsin Pharmaceutical Experiment Station, Czrcula? 9 University of Wisconsin, Bullelin 1024
I020
T H E J O U R N A L O F I N D U S T R I A L -AND EhrGINEERIiVG C H E M I S T R Y V O ~ 12. . ;NO.
During the present season Roland E. Kremers, who carried out a number of distillations for the Station, has collected and cohobated the aqueous distillates of wormwood, tansy, peppermint, and milfoil. The aqueous distillates of Monardn punctata and M . jistulosa will be collected by D. C. L. Sherk, who will also supplement Professor Miller’s study of M . $stuZosn by a parallel examination of M . punctnta. If i t required years of study to isolate and identify the oily constituents of plants, it will, no doubt, require years and years to study their water-soluble volatile constituents. If for years the writer has desircd to devote to these latter constituents such attention as they seem to merit, he has also wanted, for the same length of time, to study those products which escape from the condenser and tire not collected either in the separated oil or in the aqueous cohobate. The study of these escaping vapors will require, as experience has already shown, specially constructed condensers and absorbers. Thus will be trebled in size, as it were, this one field of phytochemistry. In bringing to your attention some of our milling and distillation problems, the writer has not attempted to solve any milling or distillation difficulties from a technological point of view, but has desired to point out how large technological operations and the biochemical study of plants should work hand in hand for the advancement of plant chemistry.
*
A COMPARISON OF ACCURACY IN ANALYSIS OF METALLURGICAL MATERIALS DURING THE PAST TWENTY-FIVE YEARS By E. D. Campbell and George F. Smith UNIVERSITY OF MICHIGAN, ANN ARBOR,MICHIGAN Received June 5, 1920
It has been only a little more than j o years since steel manufacturers realized the necessity of chemical control of their finished product, and the consequent necessity of knowing the composition of the various materials entering into the process, and the changes taking place during the various steps between the raw materials and the finished steel. During the 70’s and ~ o ’ s chemists , of many metallurgical companies developed a practice of exchanging carefully prepared and analyzed samples of steel and ores, in order to compare the accuracy of the results obtained by different chemists working on the same sample. In February 1889, the late John W. Langley, in an address before the Engineering Society of Western Pennsylvania, advocated the preparation of a set of steels which should be analyzed by a number of leading chemists in different countries and should then constitute international standardsteels. This idea Langleydeveloped in a second paper.1 Committees on analysis were formed in England, Sweden, the United States, France, and Germany. Some preliminary bulletins were prepared during the next three years and the results of the analyses, representing the work of the committees from the first three countries named, were published in the Chemical News for September 29, 1893. I t was the intention of the American committee, when the results of the analyses had been collected, to have the principal part of the American portion of the five international standard steels kept in some suitable depository, so that small samples could be distributed to such chemists as might be entitled to them. The chemical laboratory of the University of Michigan was selected as a suitable depository and the five standard steels were deposited there in September 1893. Very little of this material was ever called for, and recently a large bottle of each of the five original international standard steels was sent to the Bureau of Standards t o be kept because of their historic interest. Although analytical chemists continued t o feel the need of 1
“International Standards for the Analysis of Iron and Steel,” Trans.
Am. Inst. Mining Eng.,October 1890.
IO ,
some means of determining the accuracy of analytical methods, and the variations which might be expected between different chemists working on the same material, it was nearly ten years later that the Bureau of Standards a t Washington instituted a system of preparing carefully analyzed samples, which would cover a wider field than that of steel alone. In the summer of 1895 one of the authors gave a paper before Section C of the A. A. A. S. on “A Proposed Schedule of Allowable Differences and of Probable Limits of Accuracy in Quantitative Analyses of Metallurgical Materials.”’ The following quotation outlines the object and method of arriving a t the values shown in Table I, which are taken from a longer table in the original paper: Many methods for the determination of the various dements usually met with in metallurgical work have been proposed, each having its own claim for accuracy, or rapidity, or both, but as will be seen from the efforts of the international committee on the analysis of iron and steel, we are far from having perfect methods for metallurgical analysis. There are many sources of error in ordinary quantitative determinations, which, while they can be partially avoided, can never be wholly overcome. Among these may be mentioned such errors as arise from solubility of precipitates, solubility of apparatus in which operations are performed, impurities in chemicals, inaccurate graduation of volumetric apparatus, unavoidable error in accuracy of weighing, and last, but not least, errors due to what may be termed the personal equation, the presence or absence in the operator of that manipulative skill which distinguishes an expert from a clumsy worker. Since we cannot expect absolute agreement in results, it may be asked how close should quantitative determinations agree? This question cannot be answered by a single figure, since the unavoidable errors in the various determinations differ according to the element determined and the method used in the analysis. Just how great a difference between determinations should be allowed and what the probable limit of accuracy which may be hoped for, is largely a matter of judgment based upon the examination of the results obtained by different chemists, known to be careful operators, working upon the same material. Basing our judgment upon the usual errors of analysis, upon the commercial requirements of accuracy and upon the unavoidable sources of error we would propose the following schedule of allowable differences and of probable limits of accuracy for discussion in the section. I n the table below the first column shows the element or constituent determined; the second, a formula for calculating the difference which might be reasonably expected between the results of two chemists working upon the same material, and the third column shows a formula for calculating the probable minimum error which may be hoped for. TABLEI Allowable Difference of Per cent Iron and Steel GraDhitic carbon.. i 10.050 (0.02 X Cg)] Combined carbon in cast iron.. . . k [O.OSO f (0.02 x CC)] Carbon in steel.. , . k 0010 (0.02 x C ) l Silicon, . . . . , . . . i t0:005 (0.02 X S i ) ] Sulfur, . . . . . . . . k [0.003 (0.03 X S)l Phosphorus, . . . i [0.002 (0.02 x PI1 Manganese in cast iron and steel.. i [0.005 4-(0.04 X Mn) I Nickel.. . , . , . . . , , , k [O.OSO (0.02 X Ni)] ELEMENTOR CONSTITUENT
. . . .. . ... . Silica. . . . . . . . . . Alumina. . . . . . . Iron. . . . . . . . . . Manganese . . . . . . . Calcium oxide. . . . Magnesia. . . .. . . .. Phosphorus.. , . . .
+ + + ++ +
Probable Limit OF Accuracy
f [0.005
+ (0.005 X C g ) 1
,
,
Phos. pentoxide.
..
The object of the present paper is to bring out, by comparison of variations computed from the table with those actually found by skilled observers working on the same sample, the desirability of some such formulas for comparing the work of different analysts, and to emphasize the fact that the proportionate variations in the determination of elements, especially those occurring in small quantities, are larger than is generally realized. Undoubtedly the most valuable data for such a comparison are those given in the certificates of analyses issued by the Bureau 1
J A m . Chem SOC.,18 (1896), 3 5 .
