T H E J O l l R N A L O F I N D U S T R I A L AiVD E N G I N E E R I N G C H E M I S T R Y
io24
produced b y t h e thermal decomposition of benzene, naphthalene is not so formed. Diphenyl was undoubtedly produced in the present experiments, although no a t t e m p t was made t o isolate or identify Temp. C. 650
TABLEVI-ANALYSIS OF QUALITATIVG RZSCLTS NAPHTHALENE FORMATIOK AKTHRACEXE FORMATIOS Press. Cy- X y Tol- BenCy- X y - Tal- Ben- XaphAtm. mene lene uene zene mene lene uene zene thalene Vac. 1 12 18
i25
T’ac. 1
12
18
800
+ ++ +f -
Vac. .1 12 18 -
+++ + + ++ + ++
+
-L
t
L
+ -- ++ + + - --
it. Direct evidence was obtained of the formation of naphthalene and in some cases, notably in the benzene series, it appeared in considerable quantity in t h e cooled distillates. A N T H R A C E K E FORMATIOX-The indications of anthracene formation are not particularly satisfactory except t h a t t h e y establish t h e fact t h a t anthracene may be formed by t h e heating of t h e other hydrocarbons. Anthracene is formed with some readiness b y t h e cracking of naphthalene and it occasionally appears in t h e higher distillation cuts from t h e runs with liquid hydrocarbons. S U M MA R Y
It will be noted from t h e results of t h e
present experiments t h a t from cymene it is possible t o produce b y “cracking” all t h e other hydrocarbons of the series, such as xylene, toluene, benzene, naphthalene and anthracene. F r o m xylene results toluene, benzene, naphthalene, and anthracene b u t no cymene. Toluene yields benzene, naphthalene, and anthracene, b u t no cymene and no xylene. Benzene goes t o naphthalene a n d anthracene b u t not t o a n y of its higher homologs. F r o m naphthalene, anthracene is readily obtainable b u t none of t h e monocyclic hydrocarbons, benzene, toluene, xylene a n d cymene, are produced. Anthracene yields n o naphthalene b u t goes t o t a r r y matter, carbon a n d gas. These relations can be rendered clearer by t h e following scheme: C B H I Z - - ~CsHio, C7Hs, CsHs, CioHa, CirHlo CYMENEXylene, Toluene, Benzene, Xaphthalene, -4nthracene XYLENE+ Toluene, Benzene, Naphthalene, Anthracene ( S o Cymene) TOLUENE--+ Benzene, Naphthalene, Anthracene ( S o Cymene, Xylene) BENZENENaphthalene, Anthracene (No C v m e n e , Xylene, Tolirene) NAPHTHALENE+ Anthracene (KO Cymene, Xylene, Toluene, Benzene) ANTHRACENE +Tarry M a t t e r , Carbon and Gas (KOSapiilhalene, p t c ) .
Other compounds such as diphenyl, methyl naphthalenes a n d anthracenes, phenanthrene, etc., are undoubtedly formed b u t in the absence of identification they have been omitted from mention in t h e present connection. On the basis of the evidence a t hand it seems justifiable t o state t h a t t h e course of the cracking reaction in t h e aromatic series may be indicated as follows a n d t h a t reverse action occurs in practically negligible amount: Higher benzene homologslower benzene homolog + benzene --+ (diphenyl) -+- naphthalene ---f anthracene + carbon and gas. CHEMICAL SECTION OF THE PETROLEUM DIVISION u. s. BUREAUOF hfINES
d
v01. 7 ,
NO. 1 2
PRACTICAL METHODS FOR THE DETERMINATION OF RADIUM.’ 11-THE EMANATION METHOD By S . C. LIKD Received Pugust 31, 1915
I n a recent communication* a description was given of a n “interchangeable electroscope” and its use T i t h particular reference t o t h e quantitative determination of radium b y t h e emanation method. I n the present paper some methods are given for t h e chemical treatment a n d other manipulations involved in preparing emanation for t h e electroscopic measurements already described. One should recognize primarily t h a t there is no universal method a t present for t h e determination of radium. even when confined t o t h e emanation method. Each radioactive product requires study and ;he adaptation of a method suited t o its own peculiar chemical and physical characteristics. Nevertheless, it is sought in t h e following t o discuss some of t h e broader principles t o be followed a n d then t o unify and simplify procedures as far as is consistent with accuracy. T h e methods t o be presented are suited for use in the case of ores and the various products t h a t arise in t h e production of radium on a plant scale. Their applicability has been tested b y a large number of determinations carried out during more t h a n a year of actual operation. Other analysts will undoubtedly meet with products for which still different methods may appear better suited, and in practice modifications and improvements will suggest themselves. B u t in t h e absence of ‘published descriptions of methods of radium analysis for plant control, various procedures will be described with some minuteness in t h e following. It should be borne in mind, however, t h a t before t h e final adoption of a n y method for a given product, it will always be well t o t r y several others, selecting t h e one which appears b y comparison t o give satisfactory results with least expenditure of effort. GENERAL DISCUSSION O F PROCEDCRES
T h e underlying principle for t h e determination of radium b y t h e emanation method consists in separating radium emanation (as gas) from its parent radium in order t o measure its quantity in a gas-tight electroscope previously standardized with a known quantity of radium emanation. Analyzed pitchblende or standard radium solutions may be employed t o furnish known quantities of emanation for standardization purposes. The three following procedures may be employed in general: I-Liberate and measure electroscopically t h e emanation from a substance in which equilibrium exists between radium and radium emanation. This condition of equilibrium will, as a rule, not be fulfilled except in substances t h a t have been enclosed for a month or more in a gas-tight container. When this condition is not fulfilled, more or less emanation diffuses away and is not subject t o determination directly. I n exceptional cases radium might be conwith permission of the Director of the Bureau of Mines. THISJOWRNAL, 7 (1915). 406.
1 Published
1
Dec.,
1915
T H E JOCRATAL O F I N D C S T R I A L AND E S G I N E E R I i Y G C H E M I S T R Y
tained in a solid of such compact structure t h a t n o spontaneous loss of emanation could take place. B u t even from pitchblende the loss of ernanation (called e m a n a t i i z g p o w e r a n d expressed in terms of per cent of t h e total emanation) amounts t o a few per cent. 11-Liberate and measure the amount of emanation retained in t h e solid substance and apply as additive correction t h e e m a n a t i n g $ewer, which must be determined separately by measuring t h e emanation diffusing from t h e radioactive substance in a closed vessel. Both procedures I a n d I 1 have already been described b y t h e author in detail.’ I n practice t h e y involve long delays, a n d while suited t o scientific investigation, are not adaptable t o t h e purposes of plant control where rapidly obtainable results are essential. Whenever possible i t is preferable t o use t h e following shorter procedure: 111-By means of suitable operations (see later) remove emanation completely from t h e substance t o be analyzed for radium, close t h e de-emanated substance in a gas-tight vessel a n d allow emanation t o accumulate for a convenient period (one t o four days). After this accumulation the emanation is collected a n d measured. A time correction must be applied t o ascertain t h e maximum amount t h a t would be obtained after t h e attainment of equilibrium with the radium content. As is well known, t h e regeneration of radium emanation takes place according t o the logarithmiclaw: El = I---e-xt, where El is t h e percentage regeneration a t a n y t i m e is f , e is t h e base of t h e Naperian logarithms, a n d t h e time constant for radium emanation ( = o.oo.ij hr.-l). T h e solution of t h e function e-” for intervals of time from I hour t o 30 days will be found in the Kolowrat Table I.2 For liberation of emanation (de-emanation) a radioactive substance may be either in a state of solution or fusion. Some substances like carnotite can be de-emanated merely b y heating t o a high temperature without fusion, b u t are so changed in physical property t h a t a second ignition does not remove all t h e emanation. It is therefore evident t h a t direct ignition can be used only in case of a month’s accumulation method. T h e removal of emanation from solution m a y be accomplished b y aspiration or preferably b y boiling. Only the latter has been used a n d vrill be described in t h e present paper. The removal of emanation from a fusion is brought about b y passing air or some other gas over t h e fused mass. When possible, it is better t o bubble air through t h e melt or t o produce in it a n evolution of gas t o insure t h e complete removal of emanation. Yet another procedure t h a t has been found very useful in t h e case of carbonate fusions. in t h e absence of silica, consists in dissolving t h e cold fusion in 1-1 ”Os with evolution of CO? followed b y boiling. T h e 1 Lind a n d Whitternore, J . A m . Chem. Soc., 36, 2 0 7 2 ; also U.S . Bureau of Mines, Tech. P a p e r 86. Leon Kolourat, Le Radizrm, 6, 195-6; also Mme. Curie. Tvaill de Radioacliaild, 1, 419-20; also Chem. K a i e n d e r , 2 (1914). 361-2.
I025
further elaboration of the procedures indicated above will be found in the subsequent sections. P R O C E D U R E F O R R A D I V M I X S O L U T I O S OR I N A S O L U B L E FORM
T h e direct determination of radium in solution can be readily carried out in most cases, if certain precautions are carefully observed. These precautions are necessitated b y the oft-repeated observation t h a t radium solutions show a tendency t o lose radium from solution on standing. which is manifested b y t h e decrease in the successive quantities of emanation which can be liberated from t h e solution. This fact has resulted in the almost complete abandonment of the practice of preserving radium solutions for long periods of time for standardization purposes; and also in analytical work, this method will result in very erroneous conclusions unless special care is taken. This loss of radium from solution is t o be attributed t o t h e precipitation or adsorption of radium from solution in a form t h a t will not readily give u p its emanation. On account of t h e very small quantities of radium employed in analysis, a loss of a very small absolute quantity represents a large relative loss. The presence of precipitates or suspensions in solution should in general be avoided, although this source of error has been frequently overestimated. According t o t h e latest ideas of adsorption’ of t h e radioelements only those adsorbents are t o be guarded against, t h e negative radical of which would form with the radioelement in question a compound insoluble in t h e given solution. Accordingly t h e loss of radium b y the action of small quantities of sulfate originating in t h e glass of the container or in t h e reagents should be carefully avoided. This may be done by t h e addition of a considerable excess of “protective b a r i u m ” and t h e maintenance of a fairly high concentration of nitric acid. T h e protective action of excess of barium in radium solutions depends on t h e chemical similarity of t h e two elements, due t o which, a n y precipitant such a s sulfate t h a t would remove radium will be removed b y t h e excess of barium, or rather radium a n d barium will be precipitated in the same proportion in which they occur in solution, a n d hence the greater the excess of barium the more insignificant becomes the loss of radium. The action of nitric acid consists in increasing t h e solubility of radium sulfate a n d also in preventing the formation of a n y basic salts of radium which are formed b y the action of t h e a radiation and which would be precipitated in neutral solution. The solubility of barium nitrate in concentrated nitric acid is not very great, SO t h a t care must be taken t h a t the two shall not exceed t h e solubility product of barium nitrate in boiling solution. The two important factors in dealing with radium solutions analytically consist then in maintaining excess of barium and a rather high concentration of nitric acid. All solutions will fall into one of t h e three following classes, and the reasons for the treat1
F. P a n e t h , Ph3’sik. Z e i l . , 16 (1914), 924-9; K . Horowitz a n d F Z.p h y s i k . Ciicm., 89 ( 1 9 1 5 ) , 513-28.
Paneth,
T H E J O U R N A L OF I N D U S T R I A L d Y D ENGINEERING CHEMISTRY
1026
m e n t prescribed for each will be clear from t h e foregoing discussion: I-SOLUTIOKS
CONTAIKISG
BARIUM I N LARGE
EXCESS
OF T H E RADIUM
T a k e a suitable portion of t h e solution (to contain about I X IO-^ g. of radium) a n d add it t o I : I H N 0 3 in a small Jena flask. Add a few glass beads a n d boil for 5 t o I O minutes t o remove all emanation. Allow t o cool slightly before closing tightly with a one-hole stopper provided with a glass t u b e drawn out t o a capillary at t h e upper end. Seal off t h e capillary while some s t e a m is still in t h e flask in order t o produce a partial vacuum, which should be retained until t h e flask is again opened, t h u s affording a proof t h a t no outward leak of gas has taken place. Note t h e exact t i m e a n d date of closing the flask, and hold for accumu1at:on of emanation. 2-SOLUTIONS
CONTAINING
LITTLE
OR
KO
BARIUM
Add a suitable portion of t h e solution t o I:I "Os saturated with barium nitrate a n d proceed as in ( I ) . g-SOLUTIOKS
CONTAINING NO BARIUM B U T A K EXCESS
O F A BARIUM
PRECIPITAKT
S U C H AS
SULFATE
OR
CARBONATE
Solutions of this character, which are usually filtrates from a radium-barium precipitation, require especially careful treatment t o avoid very erroneous results, either high or low. If such solutions were boiled off and sealed directly, t h e results might be low as much as tenfold, owing t o a decreasing emanating power, continuing as long as they remained closed. This behavior has suggested t h a t the precipitation of radium a t very low concentrations, or a t a n y rate its removal, whatever t h e process, is a progressive time reaction. This same circumstance may, on t h e other hand, lead t o high results through incorrect sampling, even in t h e use of a correct chemical procedure, when, for example, too much of the fine (frequently invisible) precipitate may have been included in a given volume of liquid. This might easily occur in siphoning t h e liquid from above a sulfate precipitate if t h e sample were taken too near t h e end of t h e operation. I t is preferable t o t a k e several samples a t intervals and make a composite. P R O C E D U R E F O R LIQUIDS O F T H E THIRD cLass-.qdd a small sample of suitable volume t o a solution containing a n excess of barium and filter off t h e precipitate after allowing t o stand over night. The filtrate containing excess of barium is made acid t o t h e saturation point with nitric acid a n d treated as in ( I ) . T h e precipitate, if B a S 0 4 , is fused with 4 t o j times its weight of a I : I molar Na2C03-K2C03 mixture, a n d treated as described later for fusions. If t h e precipitate is B a C 0 3 , it is dissolved in HNO, containing enough HSSO4 t o precipitate a n amount of B a S 0 4 convenient for fusion, which is filtered off, dried a n d fused. T h e filtrate is combined wit,h t h e original a n d treated as in ( I ) . A!l t h e radium is t h e n contained either in t h e filtrate with excess of protective barium or in t h e fused precipitate. both of which fractions should be handled, both before and after t h e accumulation of radium, as nearly simultaneously as possible
1'01. 7 , NO. 1 2
(w,thin I j minutes) in order t h a t both lots of emanation can be introduced into t h e same electroscope, F U S I O N XIETHODS
If radium is contained in a substance not soluble. n aqueous or acid solution such a s a radium-barium sulfate, a fusion method is resorted t o . which may also prove more convenient even for soluble substances. Fuse a suitable quantity of t h e material in a small platinum or porcelain boat with a carbonate fusion mixture noting the exact time of cooling. Close this boat FIG.I a t once in a glass tube of the t y p e shown in Fig. I. T h e ends of t h e t u b e are drawn down so as t o accommodate rubber t u b h g , and t h e n t o capillary tips t o be broken inside t h e rubber on opening. Emanation is allo\Ted t o collect for one or more days. Connect t h e glass t u b e at one end b y means of rubber tubing t o a glass stop-cock and a t t h e other t o t h e partially evacuated emanation chamber of t h e interchangeable electroscope. Break t h e glass tips inside the rubber connections, a n d exhaust t h e air from t h e glass tube into t h e electroscope, refilling t h e glass t u b e several times b y means of the stop-cock, b u t being careful t o leave enough vacuum in t h e electroscope chamber t o accommodate the gas t o be introduced later from the further treatment of the fusion. Disconnect t h e glass tube, break i t , remove t h e boat and contents. wrap in a filter paper, and place in t h e neck of a Jena flask (as shown in Fig. 11) which is half filled with I:I H N 0 3 . After connecting t h e flask with t h e gas-burette (as s h o v a in Fig. 111), a little of t h e acid is brought into cont a c t with t h e carbonate fusion t h u s setting u p a n evplution of CO?. The stop-cock leading t o t h e gas burette is immediately opened and t h e boat a n d contents are thoroughly wet with acid a n d t h e n shaken down into the body of t h e acid. I n t h e case of large FIG. I1 fusions t h e evolution of COSbecomes very rapid a n d special precautions must be taken. B u t in t h e case of small fusions not exceeding I t o 2 grams, t h e boat m a y be brought down a t once into the acid, which is boiled as soon as t h e gas evolution begins t o slacken. All of t h e COS is of course absorbed b y t h e N a O H solution in t h e burette. T h e boiling off of t h e emanation from this point on is identical with t h a t of solutions t o be described later. For small fusions of substances containing radium in t h e order of one part per million, such as t h e usual
+->
Dec.. 1915
T H E J O I ‘ R - V A L O F I N D C S T R I A L A il’ D E N GIN E E RI S G C H E M I S T R Y
crude B a ( R a )SO, and high-grade pitchblende, of which one would fuse a sample of 20 t o 40 mg.. it has been found convenient t o employ small boats folded from a piece of platinum foil I I ; ? in. in length and 3/.4 in. broad. tvhich makes a boat about I in. long and l / r in. in cross section. The foil used is l ; in.~ thick~ and has quite a long life provided the substance fused does not contain lead. For substances much poorer in radium, porcelain boats h a r e been used, and flasks as large as a liter are required to dissolre the fusion; a gas burette with a hulb enlargement a t the top is used t o coniain a sufficient quantity of NaOH solution. In this case the fusion should not be brought down into the liquid until a considerable part of the evolution has been conducted b y manipulation of the flask. D I R E C T FL-SIOX arETIioD-If preferred one can emp!oy fusion both before and after collection of emanation, instead of dissolving t h e fusion in acid as just described. As soon as the initial fusion has cooled, it is removed from the boat b y unfolding t h e platinum foil (for which purpose the thin foil is most convenient) and put into a Jena glass t u b e of the form already described (Fig. I ) where it is held in place b y glasswool plugs. The glass-n.ool also has the advantage of reacting with t h e carbonate during the second fusion t o produce a vigorous evolution of COS which aids in t h e complete removal of emanation. If the radioactive substance is free from thorium, air may be drawn directly over the melt into t h e electroscope. A solution of NaOH is interposed before the electroscope t o prevent the introduction of a n y CO?. In this connection i t may be mentioned t h a t no gas except air should ever be introduced into t h e electroscope together with emanation, because t h e specific ionization of the various gases varies Trery much from t h a t of air, roughly in proportion t o their densities. It is also well t o place a sulfuric acid drying bulb before the electroscope and another a t the entrance t o the train t o control the flow of gas as well as for drying purposes. T o produce the second fusion, the hard glass tube after being properly connected with asbestos protectors for t h e rubber tubing, is strongly heated with a Rl6ker burner while air is being drawn through t o the electroscope. The heating is continued until t h e glass finally collapses completely, which should not be allowed t o t a k e place, however, until a large quantity of air has been passed a n d t h e vacuum is nearly refilled. I t m a y also be advantageous t o allow t h e tube t o bend into a U shape or t o constrict itself so t h a t air actually bubbles through t h e melt. Both modifications of t h e fusion method are very unfavorably affected b y t h e presence of a high percentage of silica, which increases t h e viscosity of t h e melt t h u s rendering t h e removal of emanation b y direct fusion difficult, and also makes complete solution in the acid method impossible b y t h e separation of silicic acid gel on t h e surface preventing further attack of t h e acid and producing adsorption of radium a n d radium emanation. This point is more fully discussed later under t h e method for carnotite a n d tailings.
1027
X E T H O D A N D A P P A R A T U S F O R BOILIS-G O F F A N D T R A X S F E R R I S G E M A PITAT I 0 N
Set u p apparatus as shown in Fig. 111. Wire t h e rubber connections a t -4 and B . P u t into the leveling bulb C a stick of i\-aOH z t o 3 inches long (use more in~ case ~ of large quantities of CO? t o be absorbcti). Make sure t h a t stop-cock D is closed and E open. Pour boiling water into the Leveling bulb which rapidly dissolves t h e S a O H with evolution of much heat. If t h e boiling becomes too 7-igorous place a one-ho!e stopper in t h e mouth of t h e leveling bulb t o prevent liquid from being thrown out. After complete solution raise the level until t h e gas burette is filled t o t h e upper stop-cock which is a t once closed and t h e leveling bulb lowered t o its original position. If t h e amount
FIG.111 Showing a p p a r a t u s for boiling off, collecting,and t ra mlsferrmg e rnanati on Into e l e c t r o c o p e
G
of air t o be introduced is small, some air may be left initially in the burette. Break t h e glass tip F inside the rubber tubing1 a n d slowly open D t o ascertain if there is vacuum remaining in t h e flask G. If so, close D again and begin t o heat G over a wire gauze with a Bunsen burner. Test the vacuum every few seconds and as soon as t h e pressure is outward, open D and begin to boil vigorously. Boiling is continued 5-10 minutes until live steam has raised the temperature of all the liquid in the gas burette t o boiling. After t h e boiling off is complete, remove the flame and as soon as the liquid begins t o draw back, close D , and remove the flask entirely. If desired, the flask 1 T h e glass tip F after being broken off has shown a great tendency t o be carried upward b y t h e current of steam, and in some cases has lodged in t h e stop-cock D causing serious explosions. This m a y be prevented either b y using a stop-cock of wide bore or b y placing a t I a roll of thin platinum foil, which is held in place b y constricting the glass on both sides, and prevents the passage of any solid material.
1028
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 E I V G I ~ V E E R I N GC H E M I S T R Y
may be closed again for a second accumulation of emanation, b u t usually if duplicates are desired, two or more flasks are closed originally. Evacuate t h e electroscope chamber t o a suitable degree either with a hand pump or with a n aspirator. Connect a H2S04 drying bulb L t o t h e evacuated chamber a n d t o the. gas burette, as shown in Fig. 111. Be sure t h a t stop-cock J is closed. Open t h e stop-cock of t h e electroscope for a moment t o produce vacuum in t h e drying bulb, reclose i t , slowly open E t o full width, a n d t h e n again gradually open t h e stop-cock of t h e electroscope so as t o allow gas t o pass through t h e drying bulb at a fairly rapid rate. When t h e liquid in t h e gas burette has risen exactly t o t h e point K , close E , a n d open J t o allow dry dustfree air t a k e n from outside t h e laboratory t o sweep out t h e connections for a short time. Close t h e stopcock t o t h e electroscope, open E , allow t h e liquid t o fall 4 t o 5 inches below t h e shoulder of t h e burette. Close E a n d J a n d pour out all t h e excess liquid from t h e leveling bulb C. Open again t o t h e electroscope a n d allow t h e inflowing air t o bubble from t h e b o t t o m through t h e full length of t h e liquid in t h e gas burette t o insure complete removal of whatever emanation t h a t m a y have dissolved i n t h e N a O H solution. This precaution is perhaps unnecessary, since t h e hot solution of N a O H certainly does not dissolve much emanation during t h e limited exposure, b u t i t is a precaution i n t h e direction of accuracy which can be observed without additional effort. Air is t h u s passed into t h e electroscope chamber until external pressure is restored. If desired, one 3-way stopcock m a y be substituted for E a n d J . T h e same procedure is followed in boiling off a n d in handling t h e solutions derived from dissolving a n y fusion or other solid material which one may have occasion t o dissolve directly. For example, ground carnotite or pitchblende ores may be wrapped in filter paper a n d handled i n t h e same way as shown for a fusion i n Fig. 11, applying, of course, t h e correction for emanating power already mentioned. Or t h e ore may be sealed for a month in a t h i n glass bulb which is opened b y crushing against t h e bottom of t h e flask b y tapping on t h e glass stem projecting above through a second hole in t h e rubber stopper closing t h e flask.l T o economize time two of t h e boiling a n d transferring operations can be carried on simultaneously b y one operator. CHOICE O F METHOD
I n t h e following, some indications are given as t o t h e applicability of t h e various methods just discussed t o different products t h a t frequently present themselves for radium analysis. PITCHBLENDE-High-grade pitchblende is low i n silica2 a n d readily soluble in boiling I : I "03. Therefore solution as well as fusion methods are available. Low-grade pitchblende TTith high silica content is subject t o t h e same difficulties of analytical t r e a t m e n t a s carnotite (which see). Since t h e R a / U ratio is 1 See Lind and Whitternore, J . Am. Chem. SOL.,36, 2 0 7 2 ; also U. S. Bureau of Mines, Tech. Papev 88, 13. 2 A , Becker and P. Jannasch, Jahrb. d . Radioakt. u . Electronik, 12
(191.5). 14.
Vol. 7 , NO.1 2
constant and normal ( 3 . 3 3 X IO-?) in various pitchblendes,' it may be used in calculating t h e radium from t h e uranium content. This statement also applies t o carnotite i n large a n d well sampled lots.2 C A R K O T I T E , t h e principal American radium-b earing ore, is primarily a sandstone impregnated more or less with uranium vanadate. The l a t t e r is readily soluble, together with t h e radium, in excess of boiling I : I "03. One of t h e best methods for its radioactive analysis is solution from a sealed glass tube after a month's accumulation, or ignition in a hard glass t u b e sealed under t h e same conditions. Direct solution i n hot I : I "03 saturated with B a ( N 0 3 ) 2 followed b y accumulation in a closed flask for a few days without filtering also gives approximately correct results b u t is not t o be so highly recommended a s t h e two longer methods just mentioned, On account of t h e high silica content of carnotite t h e carbonate fusion melt is very viscous at temperatures suitable for t h e use of Jena glass, hence i t is difficult for t h e r a d i u m emanation t o be liberated. Higher temperature3 or t h e direct bubbling of air through t h e melt help t o obviate this difficulty, b u t experience in this laboratory has been in general unfavorable t o t h e use of fusion methods for carnotite. Dropping t h e fusion into acid fails completely for reasons already stated. CARNOTITE RESIDUES O R TAILINGS-A~~t h e difficulties arising in t h e analytical t r e a t m e n t of carnotite are many times multiplied in its extracted residues, with t h e additional difficulty t h a t , since t h e radium has already resisted solution i t is not permissible t o apply solution methods. Fusion methods may be applied only after t h e removal of all t h e silica with H F from a t least a Io-gram sample. Usually t h e solid a - r a y method4 has been sufficiently accurate for t h e residues, which are so low in radium t h a t a large relative error produces b u t a small absolute error in estimating t h e percentage of radium extraction. A C I D F I L T R A T E S FROM O R E EXTRACTION-LiqUOrS of this character can be boiled a n d sealed directly after t h e addition of a little barium a s prescribed. Carnotite ore contains a considerable amount of barium so t h a t little more need be added. This is not t h e case for pitchblende, which contains little barium. BARIUM (RADIUM) S U L F A T E S A K D SULFIDES are fused with carbonate mixture in platinum or porcelain boats (described under Fusion Method), sealed in glass tubes for t h e accumulation of emanation, a n d are either dissolved in acid or fused again t o effect de-emanation. ,
FILTRATES WITH EXCESS O F SULFATE OR C A R B O N A T E
must be treated with observance of all t h e precautions prescribed for liquids of this character. BARIUM
(RADIUM)
CHLORIDE
( O R BROMIDE)
LIQUORS
may be treated after suitable dilution according t o Method I for liquids For solutions of fairly high-grade radium salts t h e necessary degree of dilution becomes very considerable, as much as I t o I , O O O , O O O or more, in some cases. This dilution 1 B. Heimann and W . Marckwald, Jahrb. d . Radioakt. U. Eleclronik. OR
CRYSTALS
10 (1913), 299-323. 2 Lind and Whitternore, LOG. cit. 3 H. Schlundt, T r a n s . Amey. Electrochem. Soc., 26 (1914), 170. 4 R. B. Moore and K. I ,. Kithil, U. S. Bureau of Mines, Bull. 70, 64-5.
Dec., 1 9 1 j
T H E J O r R L V A L O F I , V D C S T R I A L A N D E.VGIAlrEERISG C H E X I S T R Y
is carried out with pipettes a n d measuring flasks according t o t h e usual procedures of 1-olumetric analysis a n d with due regard for the principle of p r o tective b a r i u m a n d a c i d throughout. An unusual a m o u n t of care must be t a k e n in rinsing t h e vessels in which such large steps of dilution are carried out. I t is advisable t o have a large number of pipettes a n d flasks a n d never t o use t h e same ones through too great a range of concentration. GCxERAL-The special methods employed for t h e analysis of substances extremely low in radium cont e n t , such as rocks, soils, a n d natural waters, are beyond t h e scope of t h e present paper, except in so far as all solutions a n d waters are subject t o treatment b y the boiling off method herein described for liquids. It is believed t h a t t h e application of t h e principles t h a t have been discussed in t h e foregoing should suggest a mode of procedure for a n y other substances t h a t m a y present themselves for radioactive analysis in connection with plant control in the production of radium. B u t i t is well t o bear in mind t h a t a new method or a n old method applied t o a new product should always be checked in as m a n y ways as possible before deciding on its suitability.
u s
B U R E A UOF hfIKE'3, DEPVER, COLORADO
GASOLINE FROM HEAVIER PETROLEUM OILS B y CARLETONELLISAND A. A. WELLS Received October 11, 1915
T h e object of t h e investigation, some of t h e results of which are briefly described below, was t o determine t h e commercial feasibility of certain methods of production of gasoline a n d t h e applicability of t h e product a s a fuel for motor vehicles a n d for extraction purposes. I n t h e early days of petroleum refining, gasoline was practically a waste product and t h e object of every refiner was t o make t h e gasoline cut as low a s possible a n d t h e burning oil, or kerosene cut, as large as possible, as a t t h a t time the latter was the more valuable product. T h u s it is t h a t until very recently, kerosene of 4j0 B. (or even lighter) was considered t h e proper gravity in good refining practice, while under modern methods, this burning oil fraction is again distilled, yielding a n additional quantity of gasoline a n d affording a finished burning oil of 4 2 ' B. It was in t h e early days of oil refining t h a t t h e property of cracking was discovered. I n t h e city of Newark in 1861-62, a still man had t a k e n the gravity of his distillate a n d had fixed his fire as usual while he went t o lunch. He was detained.for several hours a n d when he returned and h a d again t a k e n t h e gravity he was surpiised t o find, instead of t h e heavy oil which he had expected was passing into his burning oil c u t , t h a t t h e runnings were lighter t h a n when he left t h e still. On repeating t h e conditions he found t h a t by banking his fires after a certain gravity h a d been reached. he could greatly increase his burning oil fraction. F r o m time t o time, stills have been constructed which h a d for their object t h e cracking of t h e heavier oils into t h e lighter burning oils. I n general, t h e mode
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of operation rvas t o allow the oil vapors t o condense on the relatively cool t o p of t h e still, from which point t h e condensed oil would drop into t h e highly heated oil a t the bottom of t h e still and be cracked b y this superheating. Later the coke still was developed. This still was charged, not with crude oil b u t with t h e heavier distillates. T h e condenser was constructed w t h traps which returned the heavy portions t o t h e still for further cracking. The operation w a s continued until t h e residue in t h e still T V ~ S reduced t o coke. T h e method has practically been abolished a t the present time on account of t h e high cost of maintenance. The bottoms of the coke stil!s became red hot during t h e operation a n d quickly burned out. It has been stated t h a t such stills were r u n even when they leaked so badly t h a t after charging, streams of blazing oil could be seen running out of opcnings in t h e still bottoms. T h e openings soon filled with coke a n d t h e leaks were t h u s stopped, until t h e coke was removed from t h e still a t t h e end of t h e run. I t is well recognized among practical oil refiners t h a t petroleum cannot be refined, even with t h e modern still, without t h e occurrence of a certain a m o u n t of cracking. As t h e quality of t h e lubricating oils is often impaired b y cracking reactions t h e modern still man must know how t o keep his fires in order t o prevent such changes as much as possible. For this reason there are times during the operation when t h e fire must be increased t o its fullest capacity, while a t other stages it must be banked t o obtain t h e best results. T h e method of firing depend? t o a great extent on t h e grade of oil in t h e still. T h e principal methods of cracking petroleum oil are embraced in Table I. TABLE I I - ~ t i l l cracking
II--Tube
pressure { A--Normal B-High pressure cracking A-Normal pressure { B-High pressure . .
111-Heating IV-Contact
1 1-Treatment I 2-Treatment
of vapors in the liauid
state with reagents, such as aluminum chloride with molten metal
Some of t h e objections urged t o each of these methods are : S T I L L C R A C K I N G U N D E R I i O R M A L PRESSURE-The cost of maintenance is very high on account of t h e excessive heat on t h e still bottoms. T h e life of a cracking still is very short and cost of renewal is high. This method has practically been abandoned b y modern refiners although its use was quite extensive at one time. S T I L L C R A C K I S G U N D E R H I G H PRESSL-RE-The same heating difficulties apply as above and added to this is t h e fact t h a t t h e size of the still is limited. Very large stills would not s t a n d t h e pressure. The life of t h e still is short, for as soon as a seam starts t o open, there is danger of an explosion. T U B E CRAcKIxG-The t w o objections are t h e local superheating of t h e tubes a n d t h e formation of carbon o n t h e t u b e walls which clogs t h e t u b e a n d tends b y carbonization t o weaken t h e metal. This is true especially a t t h e points of local superheating. HE AT1 N G
'WITH
R E A G E NT S :
A L U M I X C 31 C H L 0 RIDE-
