1142
T H E JOURNAL OF I N D C S T R I A L A N D ENGINEERING CHEMISTRY
As a n example of t h e use of t h e equation suppose it is desired t o know which of two coals, A or B:is the more economical, the prices and analyses being as fof lo w s : A Cost per long tori.. . , . . . . . . . . . . . . . . , . S 3 . 0 0 Per cent water.. , , , , , , , . , , , . , , , , , , , , 4.. 25 P e r c e n t dry ash . . . . . . _ . . . . . . , . . . . . 10.25 B t . u. per pound dry coal.. , , , . , . . . . 13,500
B
$ 3 .50 3.50 8.00 13,900
Taking 8 as t h e standard ash we obtain b y substitution in ( 5 ) $0.1044 for ,4 and $0.1167 for B as t h e relative costs per I,OOO,OOO E. t . LI. A is therefore the cheaper coal and t h e extra price of B is greater t h a n is justified by its better quality. T h e chart for t h e solution of these equations is 3 0 inches square. I t is divided b y a horizontal and a vertical line into four quadrants. On t h e horizontal axis t o the right of t h e vertical axis is indicated t h e price per long ton, a , f r o m $2.00 t o $4.40 b y $0.01 (scale, l , ’ ~ in. = $0.01). The vertical line above t h e horizoiital represents the cost per long ton dry coal, c (same scale), b u t the values are not indicated. I n the first quadrant are diagonal lines representing percentages of water from o t o 1 2 and. are plotted according t o Equation I . Any two points are plotted for each line. Zero per cent water is of course t h e diagonal of t h e square! and t h e others are above i t . Distances along t h e horizontal axis t o the left of the vertical axis represent t h e cost per long ton of dry coal corrected for ash, f (same scale as before), b u t t h e values are not indicated. I n t h e second quadrant are diagonal lines representing t h e digerence between the percentage of dry ash and t h e standard ash. I n t h e cut t h e standard ash is taken as 8 per cent and is so marked, t h e others being t h e actual percentages of dry ash. These lines are plotted according t o Equation z for positive values of ( d - e) and by Equation 3 for negative values of ( d - e ) . T h e standard ash, 8 per cent dry ash in t h e chart, is, of course, t h e diagonal of t h e square. The others are parallel and range from e - d = 4 (in the chart 4 per cent ash) 30 d - c = 19 (in t h e chart 2 7 per cent ash). On t h e vertical line below t h e horizontal are indicated t h e cost per million B. t. u. from $0.060 t o $0.180 (scale in. = $0.001). I n t h e third quadrant are diagonal lines representing t h e dry B. t. u. from 10,000 t o 15,000. They are plotted according t o Equation 4. This chart is framed with a thick glass plate with bevelled edges such t h a t t h e wooden frame comes just level with t h e face of t h e glass. I t is then fastened t o t h e wall and used in t h e following manner: A T-square with the head against t h e left side of the frame is laid along the horizontal axis and the point corresponding t o t h e price per t o n of the coal in question is marked upon it or indicated b y holding t h e t h u m b nail a t t h e point. This point is then projected vertically upward by raising the square until the point intersects the line corresponding t o t h e per cent of water. Without moving t h e square the point in t h e third quadrant where i t intersects t h e line representing the difference between t h e ash and t h e standard ash
T‘ol. 8, NO. 1 2
(or in t h e chart the per cent ash) is marked. This point is projected vertically downward b y lowering the square until i t intersects t h e line representing t h e B. t. u. The point where the edge of t h e square intersects t h e vertical axis indicates the cost per million B. t. u. Fractions of per cents, etc., are easily estimated and even when this is done the result obtained can always be checked by $0.0004. or less. ATLANTICSUGAR REFINERIES, LTD, JOHN, N E W BRTJKSWICK, CAXADA
ST.
A THERMOSTAT OR CONSTANT-TEMPERATURE CABINET FOR THE FLOUR-TESTING LABORATORY B y C. H. BAILEY Received October 11, 1915
The making of yeast-leavened bread is a biochemical process, involving the use of living cells in t h e production of the gases of fermentation. The C 0 2 which expands t h e dough is derived from certain sugars b y t h e action of t h e yeast enzyme, zymase. The activity of this enzyme, or group of enzymes, is influenced b y several factors, one of the most important of which is temperature. .‘lbersonl found t h a t 2 . 7 times as much sugar was fermented b y yeast a t 28’ as a t 18’. The other ferments in t h e dough, including the natural enzymes of t h e flour, and those due t o t h e presence of bacteria and fungi, are similarly affected b y temperature variations. It is evident therefore t h a t in making comparative tests involving the use of living yeast cells, the control of the temperature is an important item. This may be eliminated as a variable b y t h e use oE suitable thermostats or constant temperature chambers. Many laboratories are making flour tests, which embody yeast-fermentationt without adequate means for the production of maintenance of t h e proper temperature. Chambers or cabinets are in use which are not uniformly heated. Electric lamps are frequently used as t h e heating element in a manner which precludes uniform heating unless fans are employed for t h e circulation of the air. Usually no provision is made for t h e automatic control of temperature, which may fluctuate within rather wide limits, depending upon t h e vigilance of t h e operator, and the facilities which are afforded for varying t h e heat supplied. Since this laboratory has had occasion t o conduct a number of investigations requiring the use of a thermostat for dough fermentation, our attention was turned t o the construction of a n adequate device for this purpose. I t was desired t o make this of a t y p e which would not only be capable of t h e proper control, b u t which could be duplicated a t a reasonable cost, and operated b y a person without much knowledge of physics. The thermostat when completed proved so satisfactory for this purpose t h a t it is believed a description of i t , and a statement of t h e reasons governing t h e style of construction adopted, might be of interest t o others engaged in a similar line of work. The electrical heating element offers marked ad1 Aberson, Rec. traw. chim. Pays-Bas, 22 (1903), 100. Cited b y Euler, “General Chemistry of t h e Enzymes,” translated by Pope, p. 241, New
York, 1912.
Dec., 1916
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
1143
T h e doors were made 8 in. wide X I O in. high, with panes of glass 5 X 7 in. Where t h e space is limited, t h e width of t h e doors may possibly be reduced I in. each, t h u s shortening a cabinet of this capacity 6 in. The 8-in. door is more desirable, a s it reduces t h e liability of striking dishes a n d pans when introducing or removing them. Small doors are preferable t o fewer large doors because of t h e reduced exposure when t h e doors are opened t o introduce or remove t h e vessels. A space of 5 in. between t h e upper a n d lower rows of doors was provided so t h a t t h e heating coils between shelves would not be too close t o t h e doughs on either side of them. Fro
I-C~eraar
m USB
vantages over other possible sources of heat. It is clean, dependable, easy of operation a n d control, and involves no serious risks of shock or fire if properly constructed and installed. This method of heating was accordingly adopted. Neither this nor any other heating system, where a n accurate control is necessary, can be made entirely fool-proof. Some knowledge of t h e properties of electricity is desirable t o secure t h e best results. This is especially true if t h e specifications and details of construction given in t h i s paper are t o be departed from. While all t h e work of making and installing t h e heating elements in t h e cabinet in this laboratory was done by the writer, t h e services of a n electrician may be necessary when one is not familiar with such work, or where certain shop facilities are not available. The cabinet was made with sufficient space for conducting 24 baking tests simultaneously if used from PIC. 11-PIES
01 CABINST
I:0 ' ___ J
I
both sides. One face is provided with twelve doors, a n d the other has a "piano-box back" which can be removed in one piece and a face having twelve doors substituted. If t h e work of t h e laboratory is voluminous enough t o justify it, doors may be provided on both faces a t t h e outset. Where t h e cabinet can be used only from one side, the back may be glued on. A depth of 18 inches permits of setting two ordinary fermentation vessels or baking-pans one behind t h e other. This depth can be reduced if t h e cabinet is used only from one face. Any reduclion in t h e cubical contents of t h e cabinet must necessarily be accompanied b y a n increase in t h e length of wire used in t h e heating element.
The inside of t h e box is virtually an undivided space. The two shelves were made b y bending t h e ends of a//lrin. iron rods a t right angles and inserting t h e bent ends into holes provided in cleats screwed t o t h e inside of t h e box. These rods were placed a t distances of 1'/2 in. from center t o center. The cleats were located so t h a t they serve as stops for t h e doors, as shown in Fig. 111. The electrical heating elements were made by winding No. 20 AdFro 111 vance resistance wire around a '/, in. iron rod. Coils wound in this manCROPS-SECT'ON ner possess sufficient resiliency t o eliminate any considerable sagging a n d to take up t h e expansion on heating, The wire was manufactured by t h e Driver-Harris Wire Co., '' of Harrison, N. J., and has a rated resistance of 287 ohms per 1000 ft. For use on a 2zo-volt current, 2 0 coils, each 1 5 f t . long, were suspended beneath t h e lower shelf, and IO coils, each I O ft. long, beneath t h e upper shelf. The,coils were supported by porcelain knobs at a distance of 31/2 in. below t h e shelves in each instance. The end coils under t h e lower shelf parallel t h e end of t h e box at a distance of z in., while t h e other coils of this set zigzag back a n d forth across t h e box, t h e knobs t o which they are attached being 6 in. apart. The end coils of t h e upper set parallel t h e end of t h e box at a distance of 3 in., and the porcelain knobs are 1 3 in. apart. These knobs should be attached by t h e cabinet maker while t h e cabinet is in course of construction. The scheme of attachment is shown in Fig. IV. This method of distributing t h e heating elements has been found t o give reasonably uniform temperatures in all parts of t h e box. Uniform heating cannot be effected when the coils (or lamps if used) are all beneath t h e lower shelf of a two- or three-shelf cabinet, a n d there is no provision for air circulation by fans. The 400 ft. of wire has a resistance of I I j ohms, and since the 30 coils are in series, a current of 1.9amperes is drawn on 2 2 0 volts. This furnishes more heat than is necessary t o maintain t h e air in t h e cabinet a t from 28 t o 32' C. when t h e air of the room is 2 2 ' C. The
I I44
T H E J O U R N A L OF I-VDUSTRIAL A N D ENGINEERING C H E M I S T R Y
current is accordingly flon-ing only part of t h e time when the thermostat i s used under these conditions. T h e cabinet may be employed for other lines of investigation a t higher temperatures, which would be Upper She/f I
bL
0wer She4
r
Tol. 8, S o .
z2
thus arranged does not r a r y more t h a n 0 . 5 ' C if properly adjusted. The heat-regulating system may be rendered niore efficient b y having a variable external resistance or rheostat in series with t h e heating elements. While not essential, this can be employed t o reduce the number of makes and breaks occurring in t h e thermoregulator. A little experience with a thermostat enables one t o judge of the proper additional resistance t o insert b y means of the rheostat when the surrounding air temperature is known. .4 rheostat of this kind can be purchased for about $8.00, while a satisfactory one may be constructed b y anyone with mechanical ingenuity for $4.00 or even less. The cost of t h e completed thermostat IS shown below. T h e cabinet in this laboratory was built of clear cypress, although white pine could possibly be used a t a slightly reduced price. Tt was finished inside and outside with white enamel paint. T h e figures represent only t h e price of the materials. A rheostat is not included, as this is a non-essential though desirable accessory. T h e cost of winding and installing t h e heating elements is omitted as this would vary with the efficiency of t h e person employed. About 4 hours were required t o wind and install t h e coils and make the electrical connections described in this paper. COST OF COMPLCTED THERMOSTAT Cabinet ............................................ $40.00 1.25 lbs. No. 20 advance resistance wire.. . . . . . . . . . . . . . . 1.88 Thermoregulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.00 Circuit breaker or relay.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.50 2 16-c. p . carbon lamps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 0.75 1 15-ampere knife switch with fuses.. . . . . . . . . . . . . . . . . . . 25 feet No. 14 insulated copper wire.. . . . . . . . . . . . . . . . . . 0.25 3 doz. split porcelain knobs.. . . . . . . . . . . . . . . . . . . . . . . . . . 0.75 TOTAL
.........................................
$59.43
T h e writer does not claim t h a t t h e features of this cabinet possess a n y marked originality. The ideas expressed in its construction were gained from several sources. The device as finally assembled possesses a serviceability t h a t is outstanding, however. I t gives added value t o tests conducted by empirical methods, as a n y fermentation or baking test must be. No laboratory concerned with such work can long afford t o be without a uniformly heated, automatically controlled device of this character which can be obtained a t such a reasonable cost. CEREALA N D FLOUR LABORATORY DIVISIONO F -4GRICULTURAL CREMISTRY MIKKESOTA AGRICULTURAL EXPERIMCUT STATION
I' Cab,n e t
through carbon contacts in t h e relay. These contacts are moved in one direction by a spring, and in the other b y t h e electromagnets. The general scheme of the wiring system is shown in Fig. TT. The thermostat 1 Since writing this paper the No. 5 thermoregulator with condenser manufactured b y t h e Chicago Surgical and Electrical Company has been tested and found satisfactory for use in this thermostat. I t costs $10.00, a n d since no relay a n d carbon lamps are required when i t is employed, t h e cost of t h e complete thermostat is reduced b y $5.80. T h e wiring system is also simplified.
NOTE ON THE RESULTS OF ANALYSES ON FERTILIZER SAMPLES TAKEN WITH DIFFERENT STYLES OF SAMPLERS' By F. B. CARPENTER Received October 20, 1916
Having noticed the low results in ammonia on samples of fertilizer taken with the ordinary half round sampling tube, on goods which we had every reason t o believe contained t h e guaranteed percentage of ammonia, an experiment was made t o determine t h e 1 Presented a t the 53rd Meeting of the American Chemical Society, New York City, September 2 5 t o 30, 1916
