matter for the soaps stored in the glass jars only, since t,his container prevented loss of moisture from the samples and kept thein more nearly under the conditions at the time of packing and, furthermore, i t was the only container used for all the samples throughout the period of the tests. Fig. 1 gives, in the form of graphs, the data coiitained in Table TI.
An Electric Graphite Resistance Furnace' By Harry Bryan, A. L. Mehring, and W. H. Ross m R s m 01 SOILY, ~ s a i x c r o u I). .
c.
LCCTRIC fiirnaces are conveniently grouped into three classes according as the heat. is generakd in an arc, in the charge acting as a resistor, or in a special resistor. Furnaces belonging to the first two classes have many industrial applications, but are unsuited as a rule for quantitative laboratory experiments, owing to the difficulty of maintaiiiing a constant temperature for any length of time over m y considerable area of the furnace. Tlie use of special reistors permits of a much more efficient teinperature control, and most laboratory furnaces therefore belong to this class. When high temperatures are required, the special mistor is ordinarily made of graphite as in the Arsem resistunce vacuum furnace.* This furnace may be ea,-iIy and accurately controlled and is therefore adapted to a wide range of appli1%. I-I~PPLCT 01.S ~ o a n c sO N NICOT~NB CONTENI08 S o ~ ~ - N r c o r r ~ scations. Tlie heating element and the charge, however, are PYQPIRATIONS enclosed in a vacuum eharnher and the fiirna(ut is tlmeforc not suited for use in investigations in which corrosive gaes ~ i s c u s s ~ oOFu RESULTS are evolved. The Tucker fiirnace' also makes use of & cylinAn inspection of the analytical results given in Tables I drical graphite resistor' and does nnt require a vacunm, hot. and TI shows that the nicotine decreased very ra.pidly from it is not eonstriict,ed so as t,n he gastight,. The furnace the hard soda soaps, and that little or no change occurred in described in the present paper, which imnhii~twfeatures of the potash soap or in the soft soda soaps after 4 years. The semisoft soda soap, Sample D, was nearly of the same compoSitiOn chemically as the hard soaps, but owing to a difference in the process of preparation it was of a gelatinous consistemcy, smooth test,ure, and entirely free from air bubbles. The consistency of the soap appears to he the controlling factor. At any rate, the soft soaps and the one sufficiently soft to forin a uniform, gelatinous mass, retained practically their fullnii~otiiiestri~ngtli for 4years. Whether or not oxidation from contact wit,h air plays any part in causing t.he changes noted (Samples A and R),the writers have not determined. It would not appear, however, that this is of any great influence, since the samples in the jars, which were better proteoted from the air than %-em t,lie cakes wrapped in paper, decomposed to a greater extent than the samples in waxed paper. The work also shows that the decrease in micotine is not due to volatilization, as in t.he case of nicotine dust preparations, but to chemical changes, the compounds formed being retained in the mixture, as is shown by the nitrogen content of the resinous material iormed and by the fact that tlie nicotine value calculated froin the total niirogen content of the samples after different periods of storage was practically tlic same as the actual nicotine c w FED.I - F U ~ A C IAN" sivrrcnsona~SYSTEJI tent at the time of making. The work is important from a commercial standpoint in both the Arsem and Tucker furiraecs wit,lr sonic new features showing that stable fish oil soapnicotine preparations can be of construction, may be operated at ordinary, redoced, or produced, akhough apparently not in cake form. The cake incremrd pressure, and was designed particularly for such form is more satisfactory from the standpoint of packing and special reactions as those involved in t.he pyrolyt,ic t r c a e shipping, hut on the other hand the soft soap will dissolve in inent of phosphat,e rock under nonosidizir~gconditions. water much more readily and on this account is more deDIBCRIPTI~X sirable froin tlie standpoint of the consumer. Additional work is being done to determine whether or not The furnace arid switchboard system are shown in Fig. I, soaps made from fats and oils other than fish oil, with which and a longitudinal cross sectioii of the fiimaee proper is reprenicotine is incorporated, will behave in the same manner, sented diagrammaticalllly in Fig. 2 . The esterior casing A and also to obtain more information with respect to the coni- of the furnace is cylindrical in shape and constructed of position of the resinous material formed. '/+-inch sheet iron The casing is flanged at the front face ACKNOWLEDGMEKT , Received Janurry IO, 1924 2 J . -4m.Chrm. Sor., 28, 921 (1906) Credit is due J. J. T. Graham, associate chemist, InsectiI Eleilroihern. iMel. I d , 6, 227 ( 1 9 0 7 ) . cide and Fungicide Laborat.ory of the Bureau of Chemistry, 4 Hutton and Patterson, T m r . Forodog 7 0 6 . . 1 . 187 (1906); Pcltter, for assistance in the analytical work. U. S. Patents 715,50+9 (1902);814.126-7 (ISM).
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822
Vol. 16, No. 8
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
L
FIG.
%-CROSS
SECTION OF
to make a gastight joint with the sheet iron plate, B, which serves as the front of the furnace. The latter is insulated from the furnace casing by means of asbestos packing, C, and fiber bushings, D, which surround the connecting bolts, E . The flanged head and rear face of the furnace casing serve to Support the water-cooled terminals, F and F', of the graphite resistor, G . The terminals may be machined out of brass cylinders to obviate trouble from leaking, but bronze casting should also prove satisfactory. Each terminal is provided with a water inlet, H , an outlet, I, and a Aanged head, J, which can be screwed into the terminal to make a gastight connection. This is facilitated by use of lead gaskets, which fit into annular grooves in the flanged heads and terminals. The flanged head of terminal F is in turn provided with a gas inlet, K , and a replaceable window, L, which enables the charge in the furnace to be in plain view of the operator and through which readings may be made with an optical pyrometer to the temperature within the fui-nace. The flanged head of terminal F' is the same as that of terminal F except that it carries a gas outlet, M , and the use of a window is unnecessary. Each terminal is also provided with a threaded graphite bushing, N , with which i t makes close contact. The bore of each bushing is of proper diameter to make good electrical contact with the graphite resistor and a t the same time permit free motion of the resistor through the bushing. The terminals are supported in place and with lead gaskets make airtight connection with the casing of the furnace by means of screw bolts, 0, through the terminal flanges, P. The circuit leads make contact with the resistor terminals by means of clamps, Q and Q'. An amorphous carbon cylinder, R , serves as a partition to protect the graphite resistor from the material used to fill the space 8,and which may consist of any of the refractory thermal insulating materials used in furnace construction. Care should be taken that these materials are dry before placing in the furnace, as any water present will cause speedy deterioration of the resistor when heated.
OP~RATION Water is first allowed to flow through the terminals and the air in the furnace is evacuated by means of any ordinary
FURNACE
type of exhaust pump. The furnace is then filled with a nonoxidizing gas such as nitrogen and the process of exhausting and filling is repeated if desired to insure complete removal of oxygen. Variations of temperature within t h e furnace are most conveniently controlled in the ordinary way by means of a transformer and switchboard which are capable of giving a suitable range of voltages in 1-volt steps. The sliding contacts between the resistor and graphite bushings take up any expansion or contraction of the casing due to differences of temperature in the furnace without imparting a n y appreciable strain on the resistor. The addition of a charge to the furnace or its withdrawal may be quickly made by unscrewing the flanged head of either terminal. I n the same way, by removing the flanged heads from both terminals only a few minutes are required to remove a worn-out resistor and insert a new one in its place. Any fume or other volatile material which is evolved in the operation of the furnace may be collected through the outlet of the rear terminal. The accompanying table shows the rate a t which different temperatures are attained in the operation of the furnace with heating elements of different sizes: Resistor A was 85 cm. long, 77 mm. outside .diameter, and 61 mm. inside diameter; Resistor B was also 85 cm. long, 77 mm. outside diameter at each end, but only 35 mm. outside diameter in the middle for a length of 30 cm., and 25 mm. internal diameter. GRAPHITE
gernperature
c.
800 900 1000 1100 1200 1400 1600 1800 2000
RESISTORA Time of Heating a t 8.5 Volts 1197 Amp. Minutes
4 11 44 95 160
.. ..
.. ..
GRAPHITB RESISTOR B Time of Heating a$ 12.5 Volts 17 Volts
C -
9.5 Volts 486 Amp. Minutes 1.5 2.0 2.5 6.5 95.0
..
.. .. ..
--
773 Amp. Minutes
805 Amp. Minutes
i:o
6:s
..
1.2 1.5 6.0
....
27.5
..
0.7
0.8 1.0 1.6 23.0 62.0
This furnace has been in almost daily operation for over a year without requiring any alterations or repairs other than an occasional renewal of the resistor tube.
