Nov., 1914
T H E J O U R N A L OF I N D C 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
lost in causticizing t h e liquor is made up in settling time. DUST A N D H E A T LOSSES I N BURNIKG
Contrary t o t h e usual supposition, there is practically no dust produced b y a properly designed plant. At one of t h e plants now in operation t h e temperat u r e of t h e waste gases a s t h e y leave t h e kiln is maint a i n e d around 3 j o o F., which is a b o u t t h e limit even for good boiler practice. CONCLUSIOKS
T h e development of t h e long rotary kiln in t h e cement industry together with improved methods of filtration a n d dewatering have made t h e recovery of t h e lime sludge from causticizing operations a perfectly simple a n d feasible proposition. T o all soda fiber mills a n d t o most alkali works there is such a wide margin of profit t h a t a n installation cannot b u t be a profitable investment, one likely t o p a y for itself in t w o or three years. 202 SORTH C A L V E RST. T BALTIMORE, MD.
A LARGE INCUBATOR FOR LABORATORY USE By F. ALEX MCDERMOTT Received June 29, 1914
I n view of t h e large number of incubators for laboratory use which have been described or listed in t h e catalogues of dealers in chemical apparatus, i t might seem t h a t t h e design of further a p p a r a t u s of this t y p e was rather superfluous. However, t h e a p p a r a t u s here described has proven so easily a n d cheaply constructed a n d set up a n d so satisfactory t h a t i t is believed others may profit from our experience with it. T h e first incubator constructed on t h e plan here described was j ft. long, 3 ft. high a n d z f t . deep outside. T h e walls, including t o p , bottom a n d doors, were made of t w o thicknesses of one-half inch poplar, separated b y a one-half inch space; this space was filled with powdered cork. ( I n constructing further a p p a r a t u s of this t y p e , t h e writer would make this space one inch.) Four doors were provided, t h e t w o upper ones opening upward until t h e y were flush with t h e t o p of t h e incubator, where t h e y were held b y a slotted brass rod a n d pin, while t h e t w o lower doors dropped down a n d were held pendant from t h e bottom of t h e incubator. Median vertical a n d horizontal cross-pieces in t h e front of t h e box were provided, upon which were placed t h e door catches. These cross pieces were beveled a t a n angle of 45O, as were also t h e front edges of t h e box, a n d t h e doors. T h e doors t h u s formed a fairly tight joint when closed. An upright was placed against t h e back, insidg, and shelf brackets were placed between this upright a n d t h e front vertical cross-piece a n d also a t t h e ends of t h e box, inside. T h e shelves rested upon these brackets. T h e shelves were made of galvanized iron, perforated with ' / z inch holes, spaced on a b o u t 4-inch centers, a n d each shelf had two " V " shaped braces on t h e under side for t h e sake of rigidity. T h e heating a n d temperature control were both ,entirely electrical a n d both were operated on a I I O
93 9
volt lighting circuit. T h e heating (for 30' C.) was secured by means of four coils each containing j o f t . of No. 2 6 Nichrome wire, t w o sets, each set of t w o coils in series, being connected in parallel, t h e t o t a l heating current being a b o u t one ampere. I n these heating coils or elements, t h e wire was wound on a frame consisting of t w o strips '/2 inch square in cross section a n d t h e necessary length (in this case 8 inches) of heavy, hard asbestos board, spaced a t t h e desired distance (14 inches) by means of "16 inch bolts; extra n u t s on t h e ends of these bolts served as binding posts for t h e terminals. Each element was supported by cylindrical, porcelain insulating knobs, such a s are used in electrical work. Two elements were fastened t o t h e ceiling a n d t w o t o t h e floor of t h e incubator. For t h e temperature control, a zoo-ohm main line relay arranged for back contact, was connected in series with a I O w a t t carbon lamp a n d a n electrical cont a c t thermometer (Eimer a n d Amend, No. 6838) constructed for t h e desired temperature. Of course, t h e S. M. Co. incubator thermostat may also be used. The t o t a l current in t h e temperature control circuit was a b o u t 0 . 0 8 ampere. A small I I O volt motor with a 6 inch fan was placed upon t h e upper shelf a t one end of t h e incubator a n d connected in parallel with t h e sets of heating units, t o secure more even distribution of temperature. T h e contact thermometer, which was constructed t o close t h e circuit a t 30' C., actually closed it a t a b o u t 2 9 . 7 j " C. a n d t h e temperature in t h e incubator held, according t o a large incubator thermometer placed centrally, a t 2 9 . j t o 30. j o C., depending upon t h e temperature of t h e room. T h e above regulation is sufficiently close for many purposes a n d t h e range of variation would be considerably reduced in a smaller apparatus. The outside of t h e box was painted white with two coats of b a t h - t u b enamel over two coats of ordinary white paint. A number of modifications of t h e design are possible. T h e contact thermometer may be obtained so constructed as t o close t h e circuit a t a n y one of a number of points, a n d a small incubator has been constructed on this principle t o hold 4j0, j O o or j j o C. A threepoint b a t t e r y switch was provided t o c u t in a n d out t h e different leads. I n this case, a n ordinary doublewall s t e a m oven was used for t h e box a n d a single heating element was used. Instead of t h e I O w a t t lamp, it is better t o provide a n adjustable resistance, as t h e sensitiveness a n d smoothness of operation of t h e relay may thereby be improved; for this purpose t h e student's rheostat (made by Jas. G. Biddle, of Philadelphia) has been found satisfactory. A similar resistance may be employed in series with t h e heating system in order t o vary t h e temperature of t h e heating coils. The apparatus, as described, works well on direct current. On alternating current it is necess a r y t o adjust very carefully t h e tension of t h e relay spring, t h e distance of t h e poles from t h e armature, length of travel of t h e armature, etc. Attempts t o utilize t h e electrolytic valve rectifier in t h e temperat u r e control circuit were unsatisfactory. T h e humming of t h e relay on alternating current is, of course, objec-
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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
tionable, but by proper adjustment may be largely eliminated. While no trouble was experienced in t h e breaking of a I I O volt circuit a t t h e contact thermometer, using as low a current strength as here employed, i t is advantageous t o run t h e temperature control circuit on t h e secondary of a small t o y or bell-ringing transformer giving I O or 1 5 volts. T h e total cost of material of t h e large wooden box incubator was about $50.00. T h e labor cost would vary with t h e circumstances of construction. MELLONINSTITUTE OB INDUSTRIAL RESEARCH UNIVERSITY OF PITTSBURGH PITTSBURGH
A PROPOSED NEW STANDARD LOOP FOR USE IN BACTERIOLOGICAL TESTS OF DISINFECTANTS
Vol. 6 , K O . I I
from about 0 . 0 1 9 t o 0 . 0 2 1 g., according to t h e angle a t which i t was lifted from t h e solution; while t h e most unfavorable results obtained, varying t h e rate of lifting out from as slowly as possible, t o a quick jerk, was from 0 . 0 1 7 t o 0.023 g., respectively; while with ordinary care, several consecutive results of from 0.020 t o 0..021 g. were obtained. Up t o this point t h e measurement of t h e drop was made by hanging t h e wire quickly on t h e balance a n d weighing by swings. Only slight error was caused by evaporation, as t h e drop was rather large. The results with t h e cube-shaped loop appeared, however, t o justify further trials, a n d tests were now made according t o t h e method of Duyser a n d Lewis (above), i. e . , by dipping out drops of a strong iodine
B y A. D. Sr. JOHN Received July 7 , 1914
The work described herewith was undertaken with a view t o obtaining a method of transferring small quantities of a liquid from one containing vessel t o another, with rapidity a n d a fair degree of accuracy; with special reference t o t h e use of such method in t h e inoculation of broth cultures, as practised in t h e principal tests of t h e antiseptic value of disinfectants. As is pointed out b y Duyser a n d Lewis,’ t h e main objection t o these tests lies in t h e unreliability of t h e “standard loop,” which (I) transfers too small a quant i t y of liquid, i. e . , about 0.003 cc., and (2) transfers a quantity which varies as much as 80 per cent from t h e average. Tests made in connection with this paper confirmed t h e second of these objections a n d indicated t h a t t h e variation was due t o two principal causes: I-The position of t h e loop on leaving t h e surface of t h e liquid. 11-The rate of removal from t h e surface. T h e variation between removing t h e loop slowly edgewise, a n d rather quickly flat t o t h e surface, was from 0 . 0 0 2 t o 0.008 g., respectively. I n order t o obviate t h e variation due t o position two loops placed with their planes at right angles t o one another were tried; a n d this a r r a n g e p e n t gave about equal results when lifted o u t a t any angle perpendicular t o t h e supporting wire, b u t varied from t h e result when lifted out with t h e wire support vertical t o t h e surface of t h e solution. Hence a third loop was added with its plane perpendicular t o t h e wire support, giving three concentric loops, t h e plane of each a t right angles t o those of t h e other two. As a tendency of t h e drop t o break away from t h e wire a t a point farthest from t h e junction of t h e wires h a d been observed, this loop was further modified b y changing t h e spherical shape of t h e loops t o squares, joined a t t h e corners. T h e loop, or rather cage, t h u s formed, has t h e appearance of t h e outline of a cube, supported by a wire from one corner, a n d measuring about 3 mm. on a n edge. The corners should be welded rather t h a n twisted. T h e wire of t h e cube is conveniently made of No. 2 8 B. and S. Pt wire, a n d t h a t of t h e support of No. 25. This last described loop gave drops varying in weight 1
THISJOURNAL, 6 , 199.
solution, placing in distilled water, a n d titrating, using dilute thiosulfate. Eight consecutive tests gave t h e following ratio: Thiosulfate cc. 1 .................... 35 2 ..................... 36 3 .................... 36 4 .................... 35
Thiosulfate
..................
5. 6.. . . . . . . . . . . . . . . . . . 7................... 8...................
cc.
38 35 36 36
Putting t h e mean, 3 5 . g = 100.0,we get a maximum variation of 6 per cent. It will also be noted t h a t t h e volume of t h e drop carried by this loop is about 0.020 cc., or over six times. the volume given by Duyser and Lewis as t h a t of t h e present “standard loop,” t h u s overcoming largely t h e first objection advanced by them in t h e article quoted. It would therefore appear t h a t a loop such as t h e one described above would eradicate some of t h e difficulties a t present encountered in making determinations of t h e antiseptic value of disinfectants by the. methods mentioned. The valued aid of Mr. Walter Erlenkotter, of this. laboratory, in connection with t h e preparation of this: paper, is gratefully acknowledged by t h e author. STANDARD TESTING LABORATORY BOARDOR E3TIMATE AND APPORTIONMENT N E W YORK CITY
NOTE ON SUBSTITUTE FOR THE BLAST LAMP Y
B y PAULJ. Fox1 Received July 15, 1914
T o t h e many substitutes for t h e blast lamp, the, writer begs t o a d d one, which, though extremely simple, he has not seen in use in any laboratory t h a t he has visited. I t consists of a n ordinary assayer’s. crucible of convenient dimensions, of which t h e bott o m has been ground or sawed off: forming a jacket. 1 Scientist in Soil Laboratory Investigations, Bureau of Soils, U . Dept. Agriculture, Washington, D. C .
s.
