April 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
velocity produced by the tube within the foam chamber forces the mixture down the tube the surface of the liquid. I n view of the foam reflux action, fractionation is produced to some extent. As a result of numerous runs on solutions having foaming tendencies, the time for Ordinary be reduced one-ha1f to three-fourths by the use of the stillhead described.
199
LITERATURE CITED (1) Uupont, G., and Dubourg, J., Bull. Z’inst. pin, No. 31, 581-5 (1926). (2) E d d y , C. W., Chemist-Analyst, 18, 15 (1929). (3) Lehnert* u. Patent 8639031
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H.i
RECEIVEDJanuary 7 , 1932. Contribution 122, Food Research Division, Bureau of Chemistry and Soils, U.S. Department of Agriculture.
Laboratory Furnace for High Temperatures HAROLD SIMMONS BOOTH AND ROLAND WARD,Western Reserve University, Cleveland, Ohio
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OR the studies of reactions up to 1000” C. a laboratory electric muffle using a metal resistance wire is quite easily constructed. Above 1000” C., however, the difficulties of obtaining a controlled temperature increase enormously. In connection with decomposition studies a t high temperatures, it became necessary to devise and build a furnace capable of maintaining a temperature constant to * 5” in the range 1000” to 1500” C. Although a platinum wound resistance furnace is possible for such temDeratures, the cost of platinum wire for a muffle is a l m o s t prohibitive. For this temperature range “Globar” heating e l e m e n t s (silicon carbide r e s i s t a n c e rods) o b t a i n e d from the Globar Corporation, Niagara Falls, N. Y., were found to be most satisfactory. After experimentation, the furnace as shown in the plan and side elevation in Figure 1was devised and built. It is built in a sheet-iron shell 0.063 inch (0.16 cm.) thick, with bottom and sides bent from one c o n t i n u o u s piece i n t o the s h a p e of a sharp-cornered U. This shell is placed on a suitably insulated support and the front and back enclosed by sheets of transite 0.5 inch (1.27 cm.) thick. Insulation is the most important feature in the construction of a high-temperature furnace. Super X slabs FIGURE 1. LABORATORY GLO- (a coarse asbestos) were used for the layer just inside the BAR FURNACE t r a n s i t e and the iron shell, since they pack closely and are an excellent preventive for loss of heat by convection. This layer was about 1.25 inches (3.17 cm.) thick. The second layer 4.5 inches (11.43 cm.) thick, inside of this, consisted of Sil-0-Cel bricks. These bricks have excellent insulating qualities but will not withstand direct heat. The third inner layer surrounding the heating chamber itself consisted of a 4.5-inch (11.43-cm.) layer of Armstrong brick, which is a good refractory and is a fairly good insulator. The floor, side, and back of the heating chamber were made from slabs of alundum 0.5 inch (1.27 cm.) thick, cast from Alundum Cement R. A. 162. The terminal mountings and the heating elements, as
shown in Figure 1, were then mounted in the furnace. (For a description of the terminal mounting and heating elements see Bulletins A and B of the Globar Corporation, Niagars Falls, N. Y.) For the higher temperatures, an alundum roof (cast from Alundum Cement R.A. 162) in the heating chamber gave trouble by sagging. A slab of sillimanite 0,567 inch (1.44 cm.) thick (furnished by the Champion Porcelain Company, Detroit, Mich.) was found to withstand perfectly the highest temperatures attained in the furnace, and was adopted. After the roof was in place, the insulating material was built up on top of it in the order described and a sheet-iron top covered the whole, serving to hold the two sides together. The heating elements were connected in series, four elements being used, two on each side of the heating chamber. The furnace operates on a 220-volt current. The temperature was controlled by suitable rheostats connected in series with the elements.
FIGURE 2. HEATING CURVEOF LABORATORY GLOBAR FURNACE USING 0.5-INCH ELEMENTS
For temperatures from 1000” to 1260” C. it was found convenient to use the 8 by 0.375 inch (20.32 by 0.953 cm.) “Globar” elements (55 volts, 2% amperes), and for higher temperatures the 8 by 0.5 inch (20.32 by 1.27 cm.) “Globar” elements (40volts, 27 amperes). The temperature was observed by an optical pyrometer and it was found that the light emission of the “Globar” elements increased with agea factor which must be kept in mind when measuring temperatures of a “Globar” furnace. In Figure 2 is plotted the heating curve for the 0.5-inch “Globar” elements. The maximum temperature attainable
ANALYTICAL EDITION
200
with no resistance in the line was 1525’ C. and was reached after 3 hours. Higher temperatures could be obtained by the use of larger elements, but one is limited by the melting
Vol. 4, No. 2
point of the refractories. The atmosphere of the furnace chamber was found to be slightly oxidizing. RECEIVED
December 21, 1831.
Photographic Records of Vitamin D Line Tests HENRYST EVENS^ AND E. M. NELSON, Bureau of Chemistry and Soils, Washington, D. C. RAPID and economical method developed in this laboratory for obtaining photographs of vitamin D line tests has proved valuable as a means of permanently recording the results, as well as for illustrating published reports (1, 3 ) . The apparatus illustrated in Figure 1 consists of a small camera designed for direct attachment to the microscope stand. Focusing for a fixed magnification is accomplished through manipulation of the coarse adjustment of the microscope alone. Cameras of this type, differing considerably in certain optical and mechanical refinements, are made by a t least two manufacturers (Carl Zeiss, Inc., and E. Leitz, Inc.).
A
FIGURE 1. PHOTOQRAPHING APPARATUS
By use of an objective of 1 X2 t o 2 X magnification an image is obtained on a 4.5 by 6 cm. plate of approximately 5X magnification. This degree of enlargement permits the recording of one line test on each plate of sufficient magnification for precise interpretation. A plate of this size also has the advantage of economy both in cost of materials and in storage space. Incident illumination is provided by two Mazda, tubular, projection lamps (110 volts, 165 watts) mounted in porcelainlined, show-case reflectors. With this illumination, fully exposed negatives are obtained on panchromatic plates with exposures of from 1 to 3 seconds. The staining procedure followed in this laboratory conforms in general with the McCollum technic for the vitamin D line test (9). The animals are killed, and a radius is removed from each and cleaned a t once. The distal end of the bone is sectioned through the cqnter on a plane parallel with the flat surface where the distal ends of radius and ulna articulate. The two halves of the bode are at once immersed in water for 1 Working under fellowship of the National Cottonseed Products Association. The long workhg distance of this objective necessitated its attachment to the lower end of the draw tube of the microscope illustrated in Figure 1
about 15 minutes, or while an entire series of bones is being prepared for staining. They are then immersed for 1minute in 1.5 per cent silver nitrate solution, after which they are washed through two changes of distilled water to remove excess silver nitrate. The bones are then exposed in water to daylight or direct sunlight just long enough to develop a delicate straining of the calcified areas without darkening or yellowing the softer tissues. Descriptive records are then made, and the stained bones are stored in water in the dark until photographed. Undue delay in photographing often leads to difficulties, owing to degradation in contrasts through discoloration or unequaI swelling of the cut surface. For photographing, the bone is placed in the center of a 2inch (5.08-em.) watch glass and covered with a square cover slip. A sufficient quantity of boiled distilled water is run under the cover glass to just fill the space beneath it. Care must be exercised to avoid the inclusion of minute bubbles between the cover glass and the stained surface of the bone. A black background for the photograph is obtained by lowering the condenser and covering the under side of the stage with black paper from the wrappings of photographic plates. If the stained surface of the bone has become discoloredthrough long standing or over-exposure to light, a better rendering of the calcified structure is ensured by interposing a suitable filter at some position between the object and the plate. The unmounted gelatin color filters are useful, as they may easily be trimmed to a suitable size and are not likely to upset the optical arrangement of the system. It has been found desirable in this laborator r filter, or its equivalent, on the up mount for all photographs of line te the contrast of discolored specimens without detracting from the quality of photographs of bones that are not discolored. If all exposures are made through the filter, estimation of proper exposure time is considerably simplified, because the filter introduces a constant factor in determining the length of the required exposure. As panchromatic plates are used exclusively, all manipulations in the dark room are carried out in total darkness. Rapid and uniform treatment of the plates is facilitated by carrying them through the various solutions and washing water in a developing rack carrying 10 or more plates. The plate rack shown in Figure 1, designed after the one used in the British “Dallon” developing tank, was made to carry 10 plates and fits into a container known as a 4 by 5 inch glass fixing box. This type of container is also used for the rinse or hardening bath and fixing solution. The shape of this container contributes to economy in the use of the developing solution and has the added advantage of a glass cover. Proper development is attained by adhering closely to a time and temperature schedule supplied by the plate manufacturer, the time being measured by an interval alarm timer. The developing solution used is that recommended by the plate manufacturer for high contrast. A quantity of this
