Vol. 16. No. 2
INDUSTRIAL A N D ENGINEERING CHEMISTRY
156
Granular Carbon Resistor Furnaces' .
By M. M.Austin
UNIVERSITY O F ILLINOIS, URBANA,
T
WO types of granular carbon furnaces are described in
which some of the disadvantages of such furnaces have been overcome and their construction simplified. 'This discussion is given in the hope that those who have suitable transformer equipment for operating such furnaces may construct them a t small cost and use them with satisfaction in alloy or other research work requiring temperatures of d6DO" t n 1790" C . I
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FIQ.
amounts of the resistor materia1 should be put in a t one t,ime and worked down with a small rod. The inner tube must be centered so as to give a uniform section of carbon about it. The sectioned refractory support permits of the crucible being placed in the zone of maximum temperature. The horizontal type of furnace illustrated in Fig. 2 is designed to give a heating space 13 cm. in diameter and 15 cm. deep, with 200 to 700 amperes a t 20 to 40 volts. It is simpler in construction and slightlv less uniform in heating. It is built in a metal box, ea& en> of which is sheeted withtransite 1.3 cm. thick. Holes are cut to receive the electrodes, which are 10 cm. square and 30.5 cm. long. The strap iron yoke and the electrodes are insulated from the metal box by this transite sheeting and by transite washers on the inside. A 30-cm. layer of brick is laid in the bottom and the bricking is continued up the sides to the top, leaving a central trough 11.5 cm. wide which is enlarged to an opening 26 cm. square a t the center. The bricking above and below the electrode so as to give a large surface of contact with the resistor is shown in the detail, Fig. 2. A second detail, Fig. 2, shows a particularly rugged type of copper connecter which will carry the necessary current without water cooling. The central portion of the furnace is faced with high temperature alundum cement so that it will keep its shape a t the high temperatures encountered there. It can be put in place by hand without using a form. About 4 cm. should be allowed for resistor on each side and a somewhat larger space between the electrodes and tlie inner tube. To operate smoothly these furnaces must be repacked frequently, and it is therefore necessary that this be easily accomplished, Positive pressure between the electrodes and the granular carbon is also important. A convenient procedure to follow in operating a furnace of this sort is to warm it up gradyally, together with a new crucible, for 2 hours in the mormng. It will then be hot and
1-VFRTICAL GRANULAR CARBON FURNACE
The furnace illustrated in Fig. 1 is designed to give a uniformly heated space 10 cm. in diameter and 15 cm. deep. The current requirement is 200 to 400 amperes at 30 to 70 volts. The following material is required for its construction: heavy can, graphite slab, buss bar copper, high temperature alundum cement, alundum tube, cast-iron ring, wood form, crushed arc carbon passing 6-mesh and held on 30-mesh screen, and fire brick. The lower electrode is bricked in a s shown in Fig. 1,leaving a central cylindrical opening 22.3 cm. in diameter and 35.5 cm. deep. The wood form is put in place, making sure that it is centrally located with respect to the depression cut in the lower electrode, and a layer of very stiff alundum is rammed in about it to a depth of 25.5 cm. This cement can be pus$ in so dry that the form can be removed immediately and the top and bottom of the lining shaped as indicated. This lining must be made of a very refractory material. Fire brick and ordinary refractory cements will not stand the temperatures encountered a t this point. Before putting the inner tube, resistor material, and iron ring in place, the furnace should be dried out as thoroughly as possible. Small Presented before the Division of Indus1 Received August 29, 1923. trial ahd Engineering Chemistry at the 66th Meeting of the American Chemical Society, Milwaukee, Wis., September 10 to 14, 1923.
FIG. 8-HORIZONTAL
GRANULAR CARBON FURNACE
February, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
It is hoped that the current and voltage data given above will be of considerable assistance to others in building furnaces of somewhat modified design. Ease of repacking, heaby electrode connections, positive pressure on the electrodes, and solid construction in general are emphasized.
157
ACKNOWLEDGMENT The author acknowledges the aid of experience gained in the research laboratory of the National Malleable Castings Company, and the assistance of C. F. Block.
Action of Trypsin upon Diverse Leathersls2 By Arthur W.Thomas and Frank L. Seymour-Jones COLUMBIA UNIVBRSZTY, N E W YORK,
N. Y.
tested on a casein substrate, 7’ HAS been shown that It is shown that trypsin is capable of hydroryzing collagen which according to the condition the proteolytic enzyme, has been treated with aarious agents, such as gallotannin, quinone, laid down by Sherman and trypsin, catalyzes the formaldehyde, and copper sulfate. Where the tanning agent comNeun2-namely, 2 mg. of hydrolysis of collagen1**a t bines onIy with the carboxyl groups of the collagen, as with copper, trypsin acting on a casein a hydrogen-ion concentrahydrolysis is as great as with untanned collagen, and does not depend substrate a t pH = 8 a t tion pH = 5.9, and a t on the amount of tanning agent present. Where the tanning agent, 40.00’ C. for half an hour. the temperature of 40” C . such as formaldehyde and quinone, combines with the amino groups Under these conditions 2 Since the chemistry of the of the collagen, the amount of hydrolysis depends on ( a ) the nature mg. of the enzyme gave 17.7 mechanism by which collaof the linkage-i. e., the type of tannage, and (b) the amount of tanmg: of soluble nitrogen. gen combines with various ning agent combined with the collagen. Chrome collagen is not This represents a trypsin substances to form leather is hydrolyzed by trypsin. strength approximately onestill almost entirely speculathird that of the strongest tive, it seemed possible that interesting results might be obtained by subjecting collagen, high-grade commercial preparation used by Sherman and tanned in various ways, to the action of trypsin. Not only Neun. As much as 20 mg. of the enzyme tested under the would this help in elucidating the theory of tanning, but it conditions requisite for pepsin activity gave no soluble nimight also give some idea of the mechanism of tryptic hy- trogen whatever. The acidity was controlled by a buffer solution, the hydrodrolysis. The primary difficulty in the study of the hydrolysis by gen-ion concentration being determined electrometrically. trypsin of collagen which has been treated with various METHOD tannrng agents lies in the fact that most of the substances used for tanning-e. g., heavy metal salts and formaldehydeFine siftings (100 mesh) of hide powder were tanned in are very definite enzyme poisons. Nevertheless] it seemed solutions of basic chromium sulfate, quinone, formaldehyde, a t least possible that by thorough washing of the treated copper sulfate, and gallotannin, washed and dried as dehide powder all soluble and ionized matter could be removed, scribed in detail below. About 0.5 gram of tanned hide leaving merely the insoluble combination of collagen and tan- powder was placed in a 10-cc. centrifuge tube with a conical ning agent. There then seemed no reason why a more bottom, graduated in tenths of a cubic centimeter. Ten complex compound, such as that of the collagen tanning agent, cubic centimeters of the buffer solution a t pH = 5.9 conshould not be hydrolyzed by trypsin, just as collagen alone taining 0.5 per cent trypsin were added. The tubes were is hydrolyzed. It is to be remembered that these various then corked and fastened to a shake machine, rotating at 8 tanned collagen compwnds are in general characterized by r. p. m. in a water thermostat a t 40.00’ C. After rotation the fact that, unlike collagen alone, they are not attacked by for 20 minutes, the tubes were removed and centrifuged for boiling water to yield gelatin, although some-e. g., vege- 20 minutes a t 1200 “times gravity.” Control tubes in which table-tanned collagen-are not entirely unchanged by hot the trypsin was omitted were run parallel with the digestions water. There is further the possibility that the trypsin and the percentage of hydrolysis determined by comparison might; hydrolyze the tanned collagen sufficiently to liberate of the volumes. enough of the tanning agent to inhibit the further action of The accuracy obtained in this method of measurement is the trypsin by “poisoning” it-i. e., presumably by combin- limited entirely by that in reading the level in the tubes. ing with or precipitating it. With the centrifuge and the fine sifted hide powder it was Yet the possibilities of throwing light on (a) the point of possible to obtain a well-defined boundary, and the percentage attack of the trypsin in the collagen molecule, and (b) the digestions so obtained are accurate to ~2 per cent. Connature of the combination in each tannage, seemed such that sidering the insoluble nature of the substrate, the method is they warranted the employment of this method of attack. probably the most accurate available, while being reasonably rapid. It is distinctly preferable to filtering off the undiMATERIALS USED Standard hide powder was chosen as the source of collagen. gested hide powder and determining that dissolved by an The trypsin was a high-grade commercial product which was estimation of nitrogen in the filtrate, a procedure which is objectionable and inaccurate for several reasons. Only 1 Received June 25, 1923. Presented before the Division of Leather small quantities of liquid are available. It is difficult to Chemistry a t the 66th Meeting of the American Chemical Society, Milfilter off the undigested hide powder satisfaCtorily and to waukee, Wis., September 10 t o 14, 1923. 9 Prom a part of the dissertation submitted b y Mr. Seymour-Jones in obtain a clear filtrate; the degradation products of hydrolypartla1 fulfilment of the requirements for the degree of doctor of philosophy sis are in part molecularly and in part colloidally dispersed, in the Faculty of Pure Science, Columbia University, June, 1923. Conand any filtration will merely effect an arbitrary separation tribution No. 431 from Columbia University. dependent upon the size of the filter pores. More particu* Numbers in text refer to bibliography a t end of article.
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