T H E J O U R N A L O F I N D U S T R I A L A N D EIVGINEERING C H E M I S T R Y
600
is a reliable agent; its run in t h e factory has confirmed its good qualities. A is a slow-acting e a r t h ; t o obtain a n y tangible results large amounts are needed, a fact which prohibits its extended application. Another feature of t h e curves is toshow approximately how much of t h e different earths would be necessary t o obtain t h e same results. For instance t o bleach t h e oil of our experiment t o a “White Oil,” there must be used of Brands A , B , C or D , 5.8, 3.0, 2.4 or 1.0 per cent of earth, respectively. T o determine the loss of oil d u e t o absorption, 300 g. of oil were agitated with I O g. of each of t h e fuller’s earth samples for a given time a t a given temperature. T h e n t h e oil was filtered b y means of a Buchner funnel.’ When t h e earth seemed t o be dry, vacuum was kept u p for 15 min.; t h e earth was t h e n removed from t h e funnel a n d weighed. Now when there is known t h e loss due t o absorption when working with one of t h e earths, i t is possible t o figure out t h e loss t o be expected using another earth, provided t h e working conditions remain t h e same. For instance, t h e earth C was known t o cause a loss of 8 per cent; t h e presumptive losses of t h e other earths based on this figure are shown in t h e following table : FULLER’SEARTH Oil Absorbed Presumptive Loss Per cent Per cent 17.7 8.3 87.3 40.8 17.1 8.0 40.5 19.0
TABLE11-ABSORPTION OF OIL Earth plus Oil Grams A. 11.77 B . . . . . . . . . . . . . . . 18.73 11.71 D...... . . . . . . . . . 14.05
Brand . ~-
.............. c ................
T H E VALUATION
v=
d I 0 O P IO0
+-A?)
+ xAI1oo
cents,
when x is t h e percentage of earth needed, A t h e presumptive loss, P a n d 0 t h e price i n dollars for I O O lbs. of earth a n d oil, respectively; or, X A I I O Oin t h e denominator being negligible as compared with 100, t h e raw costs are simply: IO0
TABLE I11 Price(a) Presumptive Per cent of of Earth LOSS BRAND Earth for 100 lbs. Per cent $0.70 8.3 A 5.8 B $0.68 40.8 3.0 $0.79 8.0 cD . . . . . . . 2 . 4 83.15 19.0 1.0 ( a ) All prices are figured f. 0. b. Portsmouth, Va.
....... ....... ........
CONCLUSIOS
I n spite of t h e highly developed bleaching power of E a r t h D its application is not t o be recommended on account of its excessive price. A n extended use would be desirable only with t h e dropping of its price t o about $1.90 per I O O Ibs. or with a n oil price of around $4.50; in both cases t h e bleaching cost would then be about 4 cents. Brand C is t h e most economical of all; t h e higher amount of earth used is compensated by t h e low absorption. Brand B is not vie11 recommended because of its high absorption value. Finally, Brand A is not suitable for practical work on account of t h e large amount needed, which calls for large sized filter presses. I n conclusion, i t should be noted t h a t t h e work in t h e actual run is usually less costly t h a n t h e preceding figures show; t h e intense contact of earth a n d oil under pressure increases t h e effect. T o state t h a t t h e actual raw bleaching costs fluctuates between jo and 7 5 p e r cent of t h e above figures would be a fair estimate. P. 0. B o x 27, PORTSMOUTH. VIRGINIA
AN APPARATUS FOR THE PURIFICATION OF MERCURY B y HARRISON E. PATTEN AND GERALDH. MAINS Received February 2, 1917
BY
The value of fuller’s earth a n d consequently t h e economy of its use is dependent on price, bleaching power, absorption value a n d t h e utilization of t h e residue. The latter, being for all earths practically constant, may be omitted. On account of t h e impossibility of determining absolute figures for bleaching power and absorption value, t h e earth’s worth can be so ascertained t h a t i t is assumed t o bleach a n oil t o a certain lightness. The raw bleaching cost for I O O lbs. of oil is then:
Raw Bleaching Cost for 100 lbs. Cents 9.36 15.50 4.01 5.24
For t h e assumed case t h a t a “White Oil” has t o be made from o u r oil, t h e figures are collated in Table 111, t h e price of oil being taken as $11.00per I O O lbs. 1 See “Fuller’s Earth,” by Charles I ,. Parsons, Washington, D. C., Bull. 71, Bureau of Mines.
Vol. 9, No. 6
I n this laboratory we have need of mercury in a very pure state not only for standard cells, a n d calomel halfcells, b u t also in rather large quantities for t h e filling of thermoregulators used in controlling constant temperature baths. The presence of even a slight trace of foreign metal, such as lead or zinc, after t h e mercury stands a short time in contact with air, gives rise t o t h e formation of a n oxide film on t h e surface which dirties t h e capillary tubes a n d interferes greatly with t h e delicacy of t h e thermoregulator. We have tried out t h e various methods which have been proposed for t h e purification of mercury, and have used a number of t h e types of apparatus described in t h e literature. The well-known method of Lothar Meyer,’ in which mercury is passed in a fine stream through a long column of dilute nitric acid, is slow, tedious, a n d cumbersome. The speed of operation is greatly increased b y t h e modification of J. H. Hildebrand,* where t h e mercury is broken u p into numerous extremely fine streams b y passing i t through muslin into t h e acid column. L. J. Desha devised a modification3 b y which t h e mercury, after running through t h e nitric acid column, was automatically raised t o t h e t o p a n d t h u s kept in continuous circulation. Loomis and Acree4 incorporated with t h e Desha apparatus t h e means of electrolytic purification, i. e . , making t h e mercury t h e anode in a nitric acid solution.6 Even after t h e above modifications, t h e purification demanded considerable watching a n d personal attention. Also there was no means provided for renewing t h e nitric acid without cleaning a n d refilling t h e entire apparatus. We have endeavored t o construct a Z . anal. Chent., 2 (1863), 241. J . A m . Chem. Soc., 31 (1909), 933. s A m . Chem. J . , 41 (1909), 152. 4 N. E. Loomis and S . F. Acree, A m . Chem. J . , 46 (19111, 594. 5 Wolff and Waters, Bureau of Standards, Bull. 3, 623; 4 (1907), 1 . 1
2
June, 1917
T H E J O U R N A L O F I N D U S T R I A L 4,VD E L V G I N E E R I ~ V GC H E M I S T R Y
purifier which would combine t h e spraying of t h e mercury through a column of dilute nitric acid, t h e automatic return and circulation of t h e mercury. t h e electrolytic purification, a n d t h e automatic renewal of t h e nitric acid in order t o wash away t h e products of electrolysis and prevent re-solution of impurities. By means of t h e injector principle (used with some modifications of t h e Sprengel pump), t h e mercury is raised through a small-bore t u b e t o t h e t o p of t h e apparatus in small globules in a current of air. During this process some oxidation of t h e impurities takes place,' which 17-e have greatly increased b y surrounding t h e return t u b e with a heating coil. T h e purifier embodying these points has been in satisfactory operation for over eight months, during which time between j o and 60 kg. of mercury h a r e been r u n through t h e apparatus. DESCRIPTIOS O F blERCURY PURIFIER
Plans of t h e apparatus with all necessary dimensions a n d enlarged details of t h e more important parts are presented below. The complete apparatus is shown in Fig. I . I t consists of t h e following principal parts: Mercury reservoirs, nitric acid fall tube, nitric acid reservoir, spray chamber, electrodes, waste tube, injector for returning mercury, and outlet for purified mercury. Fig. z is a detail of t h e main mercury reservoir a n d of t h e spray chamber, and shows t h e placing of t h e electrodes. Fig. 3 is a detail of t h e injector, injector cup, a n d connections. The glass work can be readily assembled b y a n y glass-blower. -4 convenient s t a n d for t h e apparatus may be built from wood, or metal rods a n d clamps may be used. oPERATIox-Impure mercury is placed in t h e main mercury reservoir M , and from this flows into spray chamber S , through a stopcock which regulates t h e speed of operation of t h e apparatus. Over t h e lower end of S is stretched a piece of bolting silk which breaks t h e mercury into a fine spray upon entering t h e nitric acid. T h e silk is fastened firmly t o t h e end of S by silk thread, and a little flare at t h e end of t h e glass t u b e prevents any slipping. We have found No. 7 bolting silk very satisfactory, giving a fine spray a n d yet not readily clogging u p . A No. 20 B. & S.gauge platinum wire is fused through t h e side of' S into a mercury contact cup. This wire extends down into t h e mercury held on t h e silk. By connecting t h e wire t o t h e positive pole of a source of current, t h e mercury, as i t sprays through t h e silk, becomes t h e anode for electrolysis. The spray chamber is seated into a ground glass neck o n t h e fall t u b e F . This ground glass neck has a slot provided a t one side (Section D, Fig. 2 ) , through which t h e cathode wire is brought into t h e fall tube. T h e cathode is also KO. 20 platinum wire, and is made into a loop encircling the end of S a t t h e same level as t h e anode. An electrolyzing current of I ampere has proved satisfactory with t h e dimensions of t h e spray chamber used. T h e overflow or waste t u b e W leads from t h e fall t v b e just above t h e electrode level, so t h a t t h e products of 1
See Crafts, Bull. SOC.C h t m . Pauzs, 49, 856.
601
electrolysis are carried away b y t h e stream of dilute nitric acid. The nitric acid used is a z per cent solution. This is fed from t h e reservoir N , into t h e fall t u b e a t a slow rate, yet fast enough t o prevent clogging about t h e cathode b y separation of solid products of electrolysis, principally mercurous nitrate. I n t h e particular apparatus used, i t was found t h a t a n average rate of flow of 1000cc. of nitric acid for a 7-hour period sufficed t o maintain smooth operation. Some of t h e metallic impurities are deposited on t h e cathode. If t h e amount is excessive a silk bag placed around t h e cathode wire will prevent falling off of t h e deposit into the mercury below.' The height of t h e mercury column in t h e lower portion of fall t u b e F depends upon t h e mercury level in t h e injector cup C (Fig. 3 ) , t h e difference in level being proportional t o t h e weight of t h e nitric acid column in F . The mercury rises inside of t h e injector bulb I until i t just reaches t h e t o p of t h e inner tube. This inner t u b e is brought around up t o the top of t h e apparatus a n d is connected t o t h e laboratory vacuum system. As soon as t h e mercury rises above t h e level, ml, in t h e injector bulb, a drop falls into the inner tube and is carried in a finely divided condition b y t h e difference in pressure u p t o t h e auxiliary mercury reserin. inside diamvoir A . The inner t u b e must be of eter or less in order t o elevate t h e mercury t h e required height. A heating coil, H , surrounds t h e tube through which t h e mercury is elevated. This coil consists of a copper tube 4 f t . long, just large enough t o slip over t h e glass tube, covered with a layer of asbestos, and then wound with No. 30 nichrome wire in two sections of 19 ft., each paralleled off of a 110-volt circuit. Since t h e resistance of this wire is 6 ohms per ft., t h e current in each section is then approximately I ampere. A layer of alundum cement holds t h e wire in place a n d prevents short circuits. Outside of this is placed a second layer of asbestos for heat insulation. The finely divided mercury passing upward through the central glass t u b e in t h e coil becomes covered with a film, consisting of oxides of t h e foreign metals present a n d of mercurous oxide. The mercury from auxiliary reservoir A flows down through a tube back t o t h e main reservoir M . A stopcock in this tube serves t o keep sufficient mercury in t h e auxiliary reservoir t o prevent air being sucked in from t h e main reservoir. Also mercury may thus be held in t h e auxiliary reservoir while cleaning t h e main reservoir and spray chamber, or when inserting new bolting silk. The stoppers in t h e various tubes a n d reservoirs are of cork, except those in t h e auxiliary reservoir, which are of rubber in order t o maintain t h e partial vacuum. The optimum charge of mercury for t h e purifier is about 1 2 0 cc. or 1.6 kg. The mercury flow from the main reservoir, when regulated so as t o spray evenly a n d freely through t h e bolting silk, is approximately 30 cc. per min. Thus all of t h e mercury circulates through t h e entire apparatus about one hundred times in a 7-hour period. T h e mercury is allowed t o circulate 1
N. E. Loomis and S. F. Acree, A m . Chem. J . , 46 (1911), 5 9 5 .
T H E J O U R N A L O F I N D U S T R I A L AhTD E N G I N E E R I N G C H E M I S T R Y
602
Vol. 9 , No. 6
I
1 ;
79
:
I --i-i
I4
N t 2-DETAIL
R L ~ S E R V O I R .SPRAY ~~ CHAMBER Ground joint Bolting silk Cork stoppers Electrode slot
ne. 3
OF a, Anode c. Cathode
D ,Section
through 1-1
F/6 1. PLAN UFMEPCURY PURIf/ER M , Main Mercury Reservoir A . Auxiliary Mercury Reservoir N , Nitric Acid Reservoir V . Connection to Vacuum
three hundred times a n d is then drawn off through t h e outlet 0. At each withdrawal t h e mercury level in t h e fall t u b e F is allowed t o fall only t o a point just above t h e t u b e leading t o t h e injector cup. I n this way a constant volume of purified mercury is maintained in t h e lower portion of t h e purifier, a n d is not removed except €or cleaning t h e apparatus or shutting i t down for a long period. We have collected t h e waste nitric acid containing mercurous nitrate a n d impurities, a n d have precipitated t h e mercury with hydrochloric acid in t h e form of calomel. At t h e present high price of mercury i t is probably worth while t o reclaim t h e waste. D a t a from t h e operation of t h e purifier show t h a t there is a n average loss of 7 per cent of t h e mercury due t o solution in t h e nitric acid. From two-thirds t o
E , Electrode Leads H,Heating Coil S, Spray Chamber 0,Outlet for Purified Mercury
D E T A I L OF INJECTOR F, Fall Tube C, Injector I , Injector W , Waste Tube
CUP ml, mercury level
three-fourths of this mercury lost b y solution may b e recovered as calomel. The apparatus needs very little attention. T h e nitric acid reservoir is filled once a day, t h e mercury flow is adjusted when starting u p t h e apparatus in t h e morning, a n d looked after once in a while during t h e day, a n d t h e purified mercury is withdrawn when necessary. One piece of bolting silk usually lasts 1 5 t o 2 0 days. T h e purified mercury withdrawn from t h e apparatus may have a slight amount of nitric acid entrained. We have eliminated this b y distilling once with air bubbling through according to Hulett's method,' a n d then redistilling in vacuo, using a modification of t h e Weinhold automatic still.2 1 2
G.A. Hulett and H. D. Minchin, Piirr. Rev., 21 (1905), 388. Weinhold, Carls. Report, 9 , 68.
June,
I9I 7
THE: JOL7RiY,4L O F I N D G S T R I . 4 L AA'D E N G I N E E R I N G C H E M I S T R Y
We have used the mercury purified in this manner in our thermoregulators and found it t o give satisfactory results. Calomel half-cells made up with this mercury have checked closely with each other a n d with cells made Erom pure mercury obtained from t h e Bureau of Standards. An a t t e m p t was made by using Hulett's method' for determining small traces of impurities, t o distinguish between yarious stages of purification, b u t no clear-cut differences were obtained. BUREAUOF
CHEMISTRY, W A S H I N G T O N ,
D. C
HANDLING LABORATORY SOLUTIONS BY SUCTION By C L BEALS Received February 10, 191;
To avoid lifting heavy bottles of solutions constantly employed in t h e laboratory, a n ordinary filter p u m p provided with a few simple rubber and glass connections may be used t o advantage. The accompanying illustration shows a n adaptation of t h e idea which has been successfully applied a t our laboratory for dilute acid a n d alkaline solutions used in fiber determinations. The cumbersome supply bottles are placed out of t h e way under t h e bench. Each is fitted with a a-hole stopper (one hole acting as a n air vent) through which a glass t u b e extends nearly t o the bottom of t h e bottle. These tubes are connected by means of 3/s-in. light pressure tubing t o short glass nipples likewise extending through 2-hole stoppers of a size suitable for t h e flask in use. Nipples passing through t h e other holes of t h e stoppers are similarly connected b y rubber tubing a n d a glass Y t o t h e filter
pump. For convenience, t h e tubes leading from t h e rubber stoppers are bound together for a short distance with adhesive tape. T o handle solutions, one has now only t o place t h e stopper connected with t h e desired solution tightly into t h e service flask and s t a r t the filter pump. A vacuum tends t o form in t h e syst e m , which is made complete b y closing one branch of t h e Y by pressure of t h e fingers a t a (or a' as t h e case may be). When sufficient solution has flowed into t h e service flask i t is instantly stopped b y releasing t h e 1
G A , Hulett and H. D . Minchin, P h y s . Rei-., 2 1 (1905), 391.
pressure, thus venting t h e system. maining in t h e tubing immediately t h e supply bottle. T h e apparatus a n d does away with pouring from bothersome syphoning.
603
T h e solution redrains back into works admirably heavy bottles or
AGRICULTURAL EXPERIMENT STATIO\ AMHERST,~IASSACRUSETTS
AN IMPROVED BUNSEN DIFFUSION APPARATUS B y JEROME S MARCUS Recei\ed Februarq 27. 1917
I n a laboratory, where gas density is determined often a n d with only moderate accuracy, t h e Bunsen diffusion method has been found t h e quickest. There is no weighing, room temperature is used, a n d there are no liabilities of error from external conditions. The two chief factors of error are due t o t h e difficulty of collecting over mercury and transferring t o t h e apparatus t h e gas under investigation, and t h e irregularity of t h e action of t h e float. T h e apparatus shown in t h e sketch was designed t o eliminate both t h e float a n d t h e transference of mercury and gas, a t t h e same time securing a more uniform pressure on all determinations t h a n by the immersion method. S o t only is t h e manipulation reduced t o a minimum, b u t also the degree of accuracy increased. The glass tube A is fitted a t the t o p with a 3-way cock, opening t o t h e orifice D a n d t h e tube E . At t h e bottom i t is connected by t h e 3-way cock I , t o t h e mercury reservoir B and t h e t u b e F. T h e removable reservoir C may be a n y small vessel. For greater convenience t h e whole may be mounted on a board. T o standardize against air, cock 2 is opened to communicate w i t h E , while t h e mercury is run out of A through F by cock I . With 2 still open, I is turned t o allow mercury t o flow from B t o A till t h e meniscus reaches t h e mark z . Both cocks are then closed, and B is filled from C t o t h e mark s. At t h e same time both cocks are turned, so t h a t A opens t o D a t t h e t o p a n d B a t the bottom. By means of a stop-watch, t h e time for t h e meniscus t o move from t h e y t o t h e x is determined. T o determine t h e rate of diffusion of t h e gas for t h e comparison t o t h a t of air, 2 is opened t o E , and A filled with mercury from B through I . Cock 2 is then closed. The reservoir C is moved up t o close t h e bottom of F , which is then connected t o A b y I . This makes A t h e mercury-filled vessel in which t h e gas is collected. E is connected t o t h e source of dry gas, a n d then connected t o A b y a . T h e gas entering A drives out t h e mercury into C, against t h e difference in pressure between t h a t of t h e atmosphere a n d of t h e mercury column in A . The mercury levels are brought t o t h e marks r and s as before a n d t h e r a t e of diffusion measured. ~ ' J I \ E R S I T S OF C O L O R 4 D O
BOLLDER
