Aug., 1918
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Consideration of these effects leads t o the design of specially constructed cells.
leads
to
teeorder
the
MULTIPLE T U B E CELLS
Each of the two cells, Fig. 11, contains 6 parallel glass tubes 14 cm. long and I cm. in diameter. These tubes are joined a t each end t o bulbs containing annular shaped platinum electrodes. Each electrode has an area of 5 . 3 sq. cm. and is held rigidly in place by 4 platinum pins which are welded to the electrode and sealed into the glass wall of the cell. The cells are designed so t h a t there are no pockets in which air can collect and the sea water is admitted in such a manner as t o sweep off any bubbles which might collect on t h e electrodes. The inlet a n d outlet tubes are sufficiently large t o respond t o the maximum change in salinity. RECORDER
I n order t o secure a continuous record of salinity or concentration the Wheatstone bridge and galvanometer must be embodied in a recorder mechanism such as t h a t developed b y the Leeds and Korthrup Company. The electrical connections are as shown in Fig. 1. The most important changes in their present recorder are due t o the use of alternating current. This current may be obtained from the usual 60-cycle supply, but if only direct current is available then the small direct current motor used for driving the recorder mechanism can be equipped with slip rings a n d be operated as a converter. The recorder paper should be ruled so t h a t salinities can be read directly.
End view
r % Plan view 9 d e view
W
sea water 1 intQke
bo&
U
disckrj e
End view
Plan view
FIG.111-CONNECTIONS OF BATHAND CELLS
cell in order t o eliminate the resistance error due t o shunting the cell. S U M 11A R Y
An apparatus is described t o give a continuous record of the salinity or density of a solution by t h e measurement of its electrical conductivity. A pair of electrolytic cells is described which, when used with a suitable alternating current galvanometer, will give satisfactory operation in connection with a recorder. The temperature compensation is obtained by placing both cells, which are in the two arms of a Wheatstone bridge, in a uniform temperature bath or directly in the solution which is t o be measured. The application of this method, with such modifications in details of construction and arrangement as are necessary t o meet the needs of a particular case, is suggested for the measurement of the salinity or concentration of brines and other salt solutions and also many other substances whose composition is constant throughout changes in concentration. BUREAUOF STANDARDS WASHINGTON, D. C.
FIG. 11-ELECTROLYTIC CELL IKSTALLATION AND O P E R A T l O N
The recorder should be properly mounted in some convenient place and with insulated wires leading from it to the cells. The bells, Fig. 111,should be placed close together in a bath through which water direct from the solution continuously flows, or the cells may be immersed directly in the solution if convenient. This will insure a uniform temperature throughout the bath. A flow of water, also taken directly from the solution, should be maintained through the open cell. This flow must be broken as i t leaves the open
AN ALINEMENT CHART FOR THE EVALUATION OF COAL By A. F. BLAKE Received April 16, 1918
Some time ago the writer published a description of “A Graphic Chart for the Evaluation of Coa1,”l which, to judge from the inquiries received regarding i t , has proved of value t o a number of chemists and engineers. As a result of a recent study of nomography it has become evident t h a t the method of charting can be very much improved by the substitution of alinement principles for those of ordinary 1
THISJOURNAL, 8 (1916), 1140.
628%
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
Ac
voi.
Io, NO. a
EVALUATION OF COAL
Directions For Use By merSns of a stroight line connect the price per long ton on the left axis withthe per cent w d e r o n the inclined axis.Note the peint of interrection with. t h e 'Cost per million Btlr.* axis. Connect this point with t h e -7. dry nsk minus stondord 'lodry ash'and note t h e point o+ intersection on the l e f t asis. Connect this point with the B.t.u p e r pound dry coal on the inclined aris and y d the required result on the 'Cost per million B.t.u. aris.
analytical geometry. It may be stated as a general rule t h a t cross-section charts, though very useful for t h e visual presentation of t h e relationship of different variables, are not nearly as suitable as alinement charts for t h e purposes of numerical calculation. The latter are more compact and more easily read, are entirely self-interpolating, a n d allow less opportunity for error, since there is no necessity for projecting points first vertically and then horizontally over considerable distances. The chart given here, like t h e one previously described, is designed t o determine t h e relative values of different coals, given the price per t o n and t h e chemical analysis, by calculating t h e relative costs of a
million heat units in accordance with the methods established by t h e United States Bureau of Mines. The equations t o be solved are as follows:
j = c + -
(d-
e)2
200
f =
x=
c-0.02
(e-d)
(3)
1,000,000f
(4)
T H E JOURNAL O F INDUSTRIAL A N D ENGINEERING CHEMISTRY
Aug., 1918 IOO
a
0.02
(e--)]
[
]
1,000,000
(6)
2,240 g a = Price per long ton (in dollars) of t h e coal as received. b = Per cent water in coal as received. c = Cost per long t o n (in dollars) of t h e dry coal. d = Per cent of ash on t h e d r y basis. e = Per cent ash selected as t h e standar.d. f = Cost per l F g t o n (in dollars) of t h e d r y coal corrected for ash. g = B. t. u. per lb. d r y coal. x = Cost per million B. t. u. (in dollars). The theoretical considerations upon which these equations are based are all discussed in t h e previous paper. Equations z a n d 5 apply when t h e ash is greater t h a n standard and 3 and 6 when t h e ash is less t h a n standard.
__( d - e ) 2 is an algebraic expression 200
which happens t o represent almost exactly the price deduction t o be made for excess ash as given in t h e tables of t h e Bureau of Mines Bulletins, a n d accounts for t h e increased labor charges, diminished efficiency of combustion, etc., resulting from high ash coal. T h e values which t h e Government deducts from t h e price per t o n t o be paid we add t o t h e cost per ton. When t h e ash is below standard a premium of 2 cents per t o n for each whole ‘per cent less is paid. This explains Equation 3. Equation 5 is a combination of I , 2 and 4, a n d Equation 6 of I , 3 and 4. The tedious arithmetical calculations which would be required t o solve these equations are all eliminated by t h e use of t h e chart shown herewith. T h e directions for use are given in t h e cut. T o illustrate its use suppose i t i s desired t o know which of two coals, A or B, is t h e more economical, t h e prices and analyses being as follows: A
. . . . . . . . . . . . . . . . . . . 4.54 ................... 4.30 ................... 10.40 ............ 13,550
Price per long ton Per cent water.. P e r c e n t dry a s h . B. t. u. per Ib. d r y coal..
B $5.38 3.50 6.00 14,350
By means of a ruler, a drawing triangle, a fine silk thread, or best of all a strip of celluloid with a straight line ruled on its under side, connect 4.54 on the left-hand axis with 4 . 3 on the inclined axis. The line intersects the “Price per dry ton” axis at 4.74. If 6 is taken as the standard ash, this point, 4.74, is then connected with 4.4 on the lower part of the ash axis and the line cuts the left-hand axis again at 4.84, the cost per dry ton corrected for ash. This point is connected with 13,550 on the inclined axis and the desired result, 0.1595,read at the intersection with the “Cost per million B. t. u.” axis. Proceeding similarly with B, we obtain 0.1734 as the cost per million B. t. u. A‘is therefore the cheaper coal and the extra price of B is greater than justified by its better quality. Or, if it were desired to know what price should be charged for B to have the heat cost equal to that of A, we would start with 0 . 1 5 9 5 , the cost of a million heat units in A, and work backwards on the analysis of B obtaining $4.95. The intermediate values obtained, if not interesting, need not be noted at all, the straight line being merely pivoted over the point of intersection. The first alinement solves Equation I , the second either 2 or 3, and the third 4.
629
This chart shows how even a very complicated equation, such a s 5 , involving several multiplications and divisions, as well as additions, subtractions, and a square can be readily a n d easily solved by a properly constructed alinement chart. I t is impossible in this paper t o go into t h e mathematical details governing the construction of t h e chart, b u t t h e reader is referred t o “A Manual of Chemical Nomography” b y Dr. Horace G. Deming’ for information which should make t h e matter clear. T h e chart is, in fact, a sort of adaptation of t h e calculating device known as t h e nomon.2 ATLANTICSUGAR REFINERIES,LIMITED ST. JOHN,N. B., CANADA
NOTE ON THE USE OF THE DIPPING REFRACTOMETER B y WYATTW. RANDALL Received June 3, 19 18
Experiments recently made in this laboratory seem t o the writer t o justify the publication of a note of warning t o chemists who may have occasion t o use the dipping refractometer for exact determination of the refractive properties of liquids, especially where the latter are rather volatile. Two samples of whiskey containing a n unusually low percentage of alcohol were under examination by Mr. C. 0. Miller. The density of each of the alcoholic distillates having been detkrmined with the aid of t h e pycnometer, the refractometer reading a t 2 0 ° C. was made as a means of estimating t h e amount of methyl alcohol, should a n y be present. I n order t o prevent a n y inaccuracy of reading through evaporation of alcohol, in each case the distillate was placed by Mr. Miller in the metal cup secured by a bayonet joint to the instrumznt. The readings gave a percentageof-alcohol-by-weight which differed notably from t h a t found by the use of the pycnometer, and which indicated t h e presence in each distillate of about 1.25 per cent of methyl alcohol t o 98.75 per cent of ethyl. Similar results were obtained by two other chemists, working independently. As t h e presence of methyl alcohol in a n y noticeable amount in these whiskeys was a matter of importance, all the distillations and dkterminations were carefully repeated by Mr. Miller; while t h e general results were t h e same, t h e figures obtained were not as close as was considered necessary in a case in which much was a t stake. Accordingly, t h e writer obtained fresh distillates, determined their respective den‘sities and refractometer readings, using, however, in t h e lattsr work, glass beakers instead of the m-tal cup, in the belief t h a t evaporation would play a very small p a r t in t h e case of a 2 5 per cent alcohol a t zoo C. The beakers were of course corked while they hung in t h e bath, a n d the corks were withdrawn only when alcohol a n d refractometer prism were both unquestionably a t 2 0 ’ C., t h a t is, about after half a n hour’s immersion in the bath. The readings gave no evidence of the p r s e n c e of methyl alcohol. The original distillates were reexamined, this time using 1 2
Unirevsity Press, Champaign, Illinois. J. A m . Chem. Soc., 39 (1917), 2137.
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