Analytical Chemistry of the Less Familiar Elements Papers presented at the Sixth Annual Summer Symposium sponsored by the Division of Analytieal Chemistry and ANALYTICAL CHEMISTRW, Troy, 9. Y., June 19 and 20, 1953
Analytical Chemistry of Beryllium FR.SNK A. \-INCI T h e Brush Beryllium Co., 4301 Perkins .ire., Clecelarid 3, Ohio The analyt a1 E emistry of beryllium is reviewed. Beryllium may be detected by a quick spot test utilizing p-nitrobenzeneazo'drcinol; other color and fluorescence methods are available. Methods of separation are dealt with. A frequently used gravimetric method for the quantitative determination of beryllium employs the separation of beryllium hydroxide and ignition to oxide. Precipitation of ammonium beryllium phosphate, ignition, and weighing as beryllium pyrophosphate are also utilized. i n empirical titrimetric method depends upon converting beryllium hydroxide to weakly ionized beryllium fluoride with consequent release of an equivalent quantity of alkali. A photometric procedure is based upon a nearly specific colored lake formation with p-nitrobenzeneazo'drcinol in the presence of a sequestering agent which acts to remove interferences. Analytical procedures employed in the determination of the impurities usually present in beryllium metal are tabulated. Methods used in the analysis of ores and alloys of beryllium are summarized. Possible toxicological effects and means of guarding against them are pointed out.
B
ERYLLIUM and beryllium compounds (21) possess a generous supply of unique chemical and physical properties, which have won for this element increasing applications and widespread interest, As the use and availability of beryllium increase, more and more chemists are being confronted with analytical problems involving beryllium. Because information on the analytical chemistry of beryllium is generally scattered and somewhat controversial, this brief but orientative review of the available analytical methods has been undertaken. At the present time beryl (3BeO.AI2O3.6Si02)is the only mineral of beryllium of commercial importance. Gem-beryl (emerald or aquamarine) approaches the theoretical composition of 14% BeO, 19% Al,Oa, and 67% SiOz by weight, but commercial ore is contaminated with more or less quartz, feldspar, granite, and mica, with which it is usually associated as in pegmatite dikes. Vauquelin (48) discovered the element in 1797. The metal itself was f i s t produced by Wohler (56) (and simultaneously and independently by Bussy) in 1828. By 1897 Lebeau (84)had pro-
duced a beryllium-copper alloj n hich was to give beryllium its first industrial foothold. Beryllium is the only stable light metal with a high melting point (1285' (2.). It possesses fail strength and good electrical ronductivity, but generally poor ductility. I t is extremely transparent to x-rays (thus is used for x-ray windows). I t has low neutron capture and high neution scattei cross sections and provides a good source of neutrons (thus is applicable as a moderator or reflector in nuclear power reactors). Beryllium-copper alloys (40) are well known for their controllable precipitation hardening characteristics, unusual resistance to fatigue and impact, and nonmagnetic antisparking properties (thus they are used in precision instrument springs, diaphragms, circuit breaker parts, and gears). Beryllium oxide is especially useful in refractory crucibles because of its high melting point. high thermal with very low electrical conductivity, and good resistance to thermal shock ( S I ) . DISSOLUTION OF S4MPLE
For analytical purposes, beryllium metal is conveniently dissolved in diluted sulfuric acid. It is, however, readily attacked by all the commonly used mineral acids except nitric, which, if cold and concentrated, has little effect. Alkalies react with beryllium with the evolution of hydrogen. The hydroxide, Be(OH)2, is amphoteric, and with excess alkali it forms beryllate. This differs from the corresponding aluminate in that the former is fairly easily hydrolyzed by heating or diluting its solution. Beryllium oxide is practically insoluble in dilute hydrochloric acid, but it can be put into solution either hy boiling with sulfuric and hydrofluoric acids or by fusion with potassium bisulfate. Alloys of beryllium with copper, nickel, or cobalt are usually attacked with nitric acid; those with iron, aluminum, or magnesium are attacked with hydrochloric acid. Powdered beryl ores respond best either to fusion ($9) with sodium carbonate or to digestion with combined hydrofluoric and sulfuric acids. DETECTION
In the general qualitative scheme of analysis, the sample solution, previously freed of silica and the members of the acid sulfide group, then boiled to expel hydrogen sulfide, is treated with ammonium hydroxide to a p H of 8.5. The precipitated combined hydroxides, including beryllium, aluminum, iron, and chromium,
1580
V O L U M E 2 5 , NO. 1 1 , N O V E M B E R 1 9 5 3 are dissolved in acetic acid. The resulting solution is treated by the 8-quinolinol method to remove quinolates, which are insoluble in acetic acid-acetate buffered solution a t a p H of 5.7. The filtrate ie brought to a p H of 8.5 with ammonium hydroxide, boiled, and filtered. A white gelatinous precipitate caught on the filter paper is beryllium hydroxide and should be confirmed. The p-nitrobenzeneazoorcinol spot test for beryllium ( 2 3 ) is a suitable test. Spot Test. Khen a solution of p-nitrobenzeneazoorcinol (called Zenia) in 0.1 S sodium hydroxide is added to a moderately alkaline solution of beryllium, it turns immediately from yellow to red. This color change is the result. of a selective colored lake formation (14).
To prepare the dye solution, dissolve 0.03 gram of p-nitrobenzeneazoorcinol powder (Eastman Kodak) in 100 ml. of 0.1 Ai sodium hydroxide solution bs- stirring with a mechanical stirrer for about 5 hours. Filter anti store in a red (low actinic) glass bottle. Renew about once each month. A portion (estimated to represent 1 to 10 mg. of beryllium) of the hydroxide precipitate, obtained by the general analytical procedure, is dissolved in 10 ml. of cold 2 X sodium hydroxide solution to give the test solution. Two drops of the dye solution are placed on a double thickness of filter paper, forming a brownishyellow spot. One drop of the test solution is transferred to the center of the dye spot. A red to pink coloration confirms the presence of beryllium. The folloiving additional tcsts have been recommended io], both detection (55) :tiit1 qumtitative estimation of ber!.lliuni: 1. Quinalizarin, 1,2,~~.S-tetrahydros)-anthraquinone (15, 4 3 ) . 2 . Curcumin ($22). : 3 . .Uianin or naphth:iz:arin (.47). 4. Saphthacrome (krtxen G or Saphthachrome Azurinr~2 B 1")
1651.
5 , .iluminon (La). 6. Quinizarin, 2-~ulloiiicacid (1I ). 7. >forin, 3,j,i,Z',t'-1,eiitahydroxyflavone (39). 8. Quinizarin, l,-l-tlihydroxyanthrayuinone(16). 9. 1-Akmino-4-hydrox> anthraquinone (-55). The latter three tests tlcprnd upon fluorescence when an alkaline solution of beryllium is exposed to ultraviolet light. Compared to the p-nitroI)eiize~ieazoijrcinol test, some of the above listed tests are more sensitive, hut all suffer from considerably greater interferences. This necessitates more complete isolation of beryllium preceding their application. SEPARATIOSS
Elimination of inkrfering quantities of other elements is ofteii 5 prerequisite in the quantitative estimation of beryllium content. The following most frequently encountered methods of separation are suggested. Removal of Phosphoric Acid. Phosphates are removed (in the usual manner) with ammonium molybdate from a solution made acid with nit,ric acid. Separation of Beryllium from a Preponderance of Aluminum. Aluminum chloride is precipit,ated by the method of Gooch and Havens (42) from a concentrated solution of hydrochloric acid and &her saturated with hydrogen chloride gas. The small amounts of aluminum remaining can then be removed (if required) by means of the gquinolinol separation (18). FROM A PREPONDERANCE O F I R O X . Ferric chloride can be extract.ed by ether from a cold h~~drochloric acid solution having a specific gravity of 1.10. Alternatively, the acid solution treated with tartaric acid is rendered ammoniacal and saturated with hydrogen sulfide to precipitate the iron as sulfide. FROXA PREPONDERAWE OF COPPER. If the det.ermination of copper is not required, it is usually expedient to remove it as soluble tetramine copper complex. Sufficient ammonium hydroxidr is added to convert all of the copper to the soluble blue complex, and t'he beryllium hydroxide formed is separated by filtration. To effect complete eliminat,ion of the copper, a double or triple precipitation may be required.
1581 If the determination of the copper is required, electrodeposition on a platinum cathode from a solution made acid with nitric and sulfuric acids is most, convenient, leaving a copper-free solut.ion containing all the beryllium. FROM .4 PREPONDERASCE OF NICKELOR COBALT. Ammonium hydroside added in excess permits complete precipitation of beryllium hydroxide, leaving the nickel and cobalt in solution in a manner analogous to removal of copper. Separations by 8-Quinolinol(S). Beryllium is not precipitated as an insoluble quinolate from an acetic acid-acetate buffered solution a t a pH of 5.7. -411 the other members of the ammonium hydroxide group are precipitated, with the exception of some of the rare earths and chromium, which map be incompletely precipitated. In addition, the separation serves to remove molybdenum, tungsten, uranium, copper, nickel, cobalt, zinc, cadmium, mercury, and bismuth, as well as more or less manganese and vanadium. Separations by Mercury Cathode Electrolysis ($6). Iron, chromium, nickel, cobalt,, copper, tin, molybdenum, zinc, and lead can be removed from a solution weakly acid with sulfuric acid, leaving all the beryllium in solution. Separations from Elements Forming Insoluble Phosphates in Fairly Strong Acid Solution. Zirconium, hafnium, and t.itanium can be precipitated with monoammonium phosphate from an acid solution containing 107' of either free concentrat'ed sulfuric or hydrochloric acid solution by volume. Separations by Cupferron. Iron, titanium, zirconium, hafnium, vanadium, tantalum, niobium, and quadrivalent uranium can be precipit,ated from an ice-cold solution containing free hydrochloric or sulfuric acid (but no oxidizing agents) by means of a 6% solution of cupferron. Separation of Beryllium from Rare Earths. Elements of atomic numbers 58 to 71 and yttrium, plus scandium, actinium, and thorium can be removed as insoluble fluorides from a solution made acid with hydrofluoric acid. Complexing with Salts of Ethylenediaminetetraacetic Acid. The use of the sodium salts of ethylenediaminetetraacetic acid as sequestering agent,s can occasionally eliminate the need for some of the above separations. For example, application of the disodium salt, of ethylenediaminetetraacetic acid to bhe gravimetric determination of beryllium as the pyrophosphate and the tetrasodium salt to the phot'ometric determination of beryllium are described below. Further applications are currently being investigated. QUANTITATIVE DETERMINATIOh OF BERYLLIUM
The methods most widely used for the quantitative determination of beryllium include: 1. The gravimetric methods, used when accuracy takes precedence over speed and ease of analysis. a. Precipitation of beryllium hydroxide and ignition to BeO. b. Separation of beryllium ammonium phosphate and ignition to Be2PBO7. 2. The volumetric "empirical titrimetric" procedure is applied when beryllium is the major constituent, the aluminum content is h o n m and small, and interfering elements are absent. 3 . The photometric p-nitrobenzeneazoorcinol method is used for the estimation of milligram or microgram quantities of beryllium. After this article was prepared, the author's attention was called to a German work on the analytical chemistry of beryllium by Fresenius and Jander (1 7 a ) , which discusses the gravimetric determination as hydroxide, sulfate, and phosphate; acidimetric and iodometric volumetric determination; colorimetric determination using quinalizarin and curcumin; determination of beryllium in minerals and alloys; and polarographic and spectrochemical determinations. Methods of separation from aluminum, iron, and other metals are given in detail. Precipitation of Beryllium Hydroxide and Ignition to Beryllium
ANALYTICAL CHEMISTRY
1582 Oxide. This method, although widely used, contains many pitfalls. With the proper recognition of and the careful precaution against these pitfalls, it is capable of highly accurate results. The solution from which beryllium hydroxide is t o be finally precipitated must be free from all other members of the ammonium hydroxide group. The prepared solution is generally obtained, after prior removal of previous groups and citrates,
calcium, iron, aluminum, copper, and a slight excess of the chelating agent their interference. Beryllium (being a t a p H of 5 to 5.5 by this excess) can very little loss.
nickel, is roughly known, can be added to remove only slightly sequestered then be precipitated with
The hydroxides, containing from 1 to 10 mg. of beryllium, are precipitated a t a p H of 8.5 with ammonium hydroxide, filtered, and dissolved back into the original beaker with dilute sulfuric acid, The solution is diluted to 100 ml. and adjusted to p H 2. Five milliliters of 15% diammonium phosphate solution and a slight excess of 15% disodium salt of ethylenediaminetetraacetic acid solution (both solutions previously adjusted to a p H of 5.5) are added. Ammonium acetate solution is added to a p H of 5.5. The solution is simmered a t just below boiling for 5 to 10 minutes and cooled in a water bath for 0.5 hour. The granular precipitate is filtered, redissolved, and reprecipitated by using only 1 ml. of each of the two reagents. Final weighing after ignition a t 1000" C. is as Be2P207( 1 ) . Wt. of Be = wt. of Be2P207 X 0.0939 VOLUMETRIC DETERMINATION OF BERYLLIUM BY EMPIRICAL TITRIMETRIC METHOD
Beryllium can be completely precipitated as hydroxide from its sulfuric (or hydrochloric) acid solution at pH 8.5. If an excess of sodium fluoride is then added, the beryllium hydroxide is converted to very weakly ionized beryllium fluoride, liberating the hydroxyl ions as sodium hydroxide:
t.
PH + 2NaOH -+ Be(OH)2 + Sa2SOd 8.5 Be(OH)2 + 2 S a F +BeF2 + 2XaOH
BeS04
carbonates, fluorides, and phosphates, by precipitating the group members (beryllium, aluminum, gallium, indium, chromium, iron, selenium, actinium, titanium, zirconium, hafnium, thorium, niobium, tantalum, protactinium, and uranium plus the 16 rare earth elements of atomic numbers 58 to 71 inclusive, and yttrium) with freshly prepared ammonium hydroxide in the presence of ammonia salts a t a p H of 8.5, and then removing all of these but none of the beryllium (see methods of separation). The beryllium hydroxide finally reprecipitated is dried and then slowly decomposed to oxide a t temperatures gradually rising to 700" C. (appreciable losses of beryllium oxide occur when it is heated at temperatures in excess of 700" C. in the presence of moisture) (20). The beryllium oxide is then ignited only once a t 1100" C. for a minimum of 1 hour, cooled in a desiccator (preferably over anhydrous magnesium perchlorate), and quickly weighed as "impure" BeO. This always contains slight amounts of silica picked up from the glassware and reagents and may contain alumina. Oxides of other metals may also be present, owing to incomplete prior removal. All of these should be determined and their combined weights deducted from that of the impure beryllium oxide.
This released alkalinity, determined by titration n-ith standardized sulfuric acid solution, can be taken as a measure of the amount of beryllium present. dluminum reacts in a similar
n
Ah
Wt. of Be = wt. of B e 0 X 0.3603 Phosphate Method in Presence of Chelating Agent. Precipitation of beryllium ammonium phosphate with subsequent ignition to beryllium pyrophosphate has the advantage of giving almost four times as much mass to weigh per equivalent beryllium content as the beryllium oxide method. Prior removal of phosphates is not required, and the precipitate being somewhat granular, occlusion of impurities is less troublesome. If the conditions of precipitation are not meticulously controlled, slight departures from constant theoretical beryllium pyrophosphate composition may occur, resulting in loss of accuracy. By taking advantage of the selective-order sequestering power of the disodium salt of ethylenediaminetetraacetic acid (go), arduous complete removal of many metal ions from the solution, prior to the precipitation of beryllium ammoniumphosphate, can be omitted ( S 4 ) . If the amount of these metal ions, like magnesium,
Figure 2. Potentiometric Titration Setup for Determination of Total Beryllium A.
1 N sulfuric acid titrant from raised reservoir
E. Automatic bottom-fill 50-ml. buret
Water jacket around buret Thermometer E . Bottle for buret overflow F. Reference calomel electrode G . Glass electrode H. Magic eye end-point indicator I. Fisher Titrimeter control unit C. D.
V O L U M E 2 5 , N O . 11, N O V E M B E R 1 9 5 3 manner; therefore it must be absent or corrected for if present. Zirconium, hafnium, rare earths, uranium, and thorium interfere and must be absent. I n practice, the above reaction does not seem to take place stoichiometrically, perhaps because of such complicating factors as the amphoteric character of beryllium. However, if the conditions of the titration are closely duplicated, the method, although empirical (27), becomes very useful because of its accuracy and relative speed. The titration must be performed precisely and slowly, giving sufficient time for the reactions to come to equilibrium. The 1 S titrating acid is standardized in terms of beryllium equivalent by using a portion of the acid solution to titrate the alkalinity released from an aliquot portion of standard beryllium sulfate solution (of gravimetrically predetermined beryllium content). Figure 1 shows the potentiometric titration curve obtained when 0.2 gram of beryllium as beryllium sulfate is treated by the empirical titrimetric procedure. Figure 2 is a schematic diagram of the equipment used in obtaining the curve.
1583 grams of sodium borate pentahydrate, and 14.35 grams of sodium hydroxide are dissolved in water and made up to 100 ml. Zenia Dye Solution. p-Nitrobenzeneazoorcinol powder (Eastman Kodak, 0.075 gram) is dissolved in 250 ml. of 0.1 N sodium hydroxide solution by stirring with a mechanical stirrer for 5 hours, filtered through an asbestos mat, and stored in a red (low actinic) glass bottle. Versene T Solution, 13.9%. A 55.501, water solutlon of Versene T [a blend of tetrasodiumethylenediaminetetraacetate and triethanolamine available from the Bersworth Chemical Co. (6)1 . is diluted 1 volume with 3 volumes of distilled water. ~
I.
PHOTOMETRIC DETERMIKATIOR- OF BERYLLIUM
When a solution of p-nitrobenzeneazoorcinol (33, 46) in 0.1 S sodium hydroside is added to a moderately alkaline solut'ion containing beryllium, a red-brown lake results. The absorption of light by this colored comples does not strictly f o l l o ~Beer's law, but by careful control and duplication of conditions such as optimum alkalinity, amount of foreign ions, dye strength. and temperature, the relationship of light absorption to beryllium content can be accurately fixed. This provides a photometric method for the estimation of beryllium cont,ent. Correct alkalinity, the range of which is small and critical, is maintained by means of a sodium borate-citrate buffer. The dye is nearly specific for beryllium, reacting in an int,erfering manner only with magnesium and to a much smaller extent with zinc. Metals like copper, nickel, iron, and calcium which form colored ions or precipit.ates in the alkaline solution, as well as zinc and magnesium, are rendered inactive t'hrough formation of soluble nonionic chelat,es if present in limited amounts.
Table I . Determination 1. Total Be 2. Total Fe
Analysis of Beryllium Metal
A\.erage Analysis, P. P. 11. 99.1% 1350
3.
Total -41
300
4.
Total .\In
1.30
5.
Total Cr
100
10. E 11.
Be0
12.
Be&
13. 14. 15. 16.
BesSz HzO -4g Co l i . Cd 18. P b 19. Zn 2.0. Li 21.
Ca
Method of Determination Volumetric, empirical titrimetric Photometric, thiocyanate or ophenant hroline Fluorimetric Pontochrome BlueBlack R ; 'Gravimetric; or colorimetric Al-quinolate Photometric, permanganate, persulfate oxidation Photometric. diohenvlcarbazide. oeriodate bxidation "
0.14%
Photometric. molybdenum blue Methyl borate distillation and turineric colorimetric Dry HC1 gas evolution, followed b y p-nitrobenzeneazoorcinol colorimetric Evpcution of methane and ignition to
0 02% 0 15% 3 3 0.2 30 30 0.3
Micro-Kjeldahl Hz evolution and ignition to HzO Polarographic or spectrographic Polarographic or spectrographic Polarographic or spectrographic Polarographic or spectrographic Polarographic or spectrographic Spectrographic or b y flame photonie-
40
Spectrographic
800
0 5 0.80%
GO2
+-.. Y
'U
Reagents. Standard Beryllium Solution. Using beryllium metal powder of known assay and dissolving by means of 20 ml. of 1 to 1 sulfuric acid per gram of metal, a solution to contain 0.Oi2 mg. of beryllium in 1 ml. is made up. Buffer Solution. Sodium citrate dihydrate (17.8 grams), 8.5
*ILLleIAY$
lrlirillYY
OilDC
Figure 3. Photometric p-Nitrobenzeneazo6rcinolMethod for Estimation of Beryllium Content Sample calibration curve
Procedure. The cooled sample solution containing from 0.06 to 1.1mg. of beryllium and no more than 5 mg. of magnesium, 20 mg. of calcium, 10 mg. of iron, or 35 mg. of aluminum is adjusted to a volume of 35 mk, Five milliliters of Versene T solution are added and the p H is adjusted to 5.5. After 5 minutes, 10 ml. of buffer solution are added, Five minutes later, exactly 10 ml. of p-nitrobenzeneazoorcinol solution are added. The solution is made up to 100 ml., mixed, and allowed to stand 10 minutes. The transmittancy is finally determined with the spectrophotometer adjusted to 100% transmittance with a reagent blank. -4515r n w wave length and a 20-mm. light path cuvette are employed. The milligrams of beryllium present are determined from a previously constructed calibration curve. Figure 3 shows a sample calibration curve obtained with a Klett-Summerson photoelectric colorimeter utilizing a green (Yo. 54) filter and a 20-mm. light path cuvette. ANALYSIS OF BERYLLIUiM METAL
Table I &ewesto summarize a typical chemical analysis of an average sample hot pressed from powder beryllium metal and t o indicate t,he method of determination (3, 9, l S , SO, 35-38, 44,4S, 61, 64). Determinations 1 t,o 8 are performed on individual aliquot:. of a single sulfuric acid solution of the sample. Determinatioris 9 to 14 are performed on individual portions of metal sample. Determinations 2 to 9 and 15 to 21 can he performed spectrographically. Determinations 1 and 10 t,o 14 are performed only by wet chemical methods. Det'ermination 14 refers only t o beryllium metal powders. Of t,hese methods, the beryllium oxide and beryllium carbide procedures are unusual and need further description. Determination of Beryllium Oxide in Beryllium Metal. The determination of beryllium oxide in beryllium metal is based upon thefact t,hat at temperatures of 520" to 800" C. d r y hydrogen chloride gas will, when passed over beryllium metal, convert it t,o beryllium chloride, which is volatilized off: Be
+ 2HC1-+
800" C .
BeCls
+ H,
ANALYTICAL CHEMISTRY
1584 The beryllium contents of both beryllium carbide and beryllium nitride are also volatilized o f f RS beryllium chloride: Be&
+ 4HC1+ 2BeC1, + CH, + S I C 1 -+ 8ReC12 + 2NH4C1
Be3nT2
The beryllium oxide content is unattacked and remains as :L residue in the boat. It can be put into solution and the quantity present ascertained by the photometric method. Figure 4 shows the equipnient uwd in carrying out the above determination. I
C C : E F H I d L i / C Figure 4. Apparatus for Determination of Beryllium Oxide Content in Beryllium Metal by Dry IIydrogen Chloride Gas Evolntion Method A
Heliuin gas inlet
B.' 250-ml. separatory funnel filled with hydrochloric acid
C. 2-liter filter flask half filled with concentFated sulfurlo acid 30-inch rnercurv manometer a n d reservoir %O&-: &-Ek pirtially filled with concentrated sulfuric acid
-n.
E F'
Drying tower filled with anhydrous magnesium perchlorate C: Clear quartz tube, '/B inch in outside diameter and 22 inches long, with side arm near open end and orifice s / ~ iinch in diameter a t opposite end H. Hevi-duty tube furnace, temperature varied from 600' to 800" C. I. IIevi-duty tube furnace niitintained a t 900' to 1000" C. J . Fused quartz tube, 1.25 inches in outside diameter. 1 inrh in inside diameter, 30 inches long, reduced end K , L , M . 500-ml. flasks. I, rontains Concentrated sulfuric acid .V. To water aspirator 0. Water manometer
ployed where higher accuracy ia demanded. These are recommended only in the case of beryl ores containing more than 1% beryllium oside. Alloys of Beryllium (50). Beryllium-copper alloys are the most industrially important alloys of beryllium. These include Master-alloy cont,aining 4 t804.25% beryllium with about 0.1% iron, 0.06% aluminum, and 0.08% silicon as impurities and the ternary alloys employing nickel or cobalt hardener and made from the Master-alloy. The most common of these contain about 2% beryllium with 0.35% nickel or cohalt and 0.25y0 beryllium with 2% nickel or cobalt. The beryllium in the above alloys can be determined t)y any of the methods given. When the spectrophotometric procedure is used, the size of sample should he chosen to contain about) 0.3 mg. of beryllium. However, at least 1 gram of the metal sample should be dissolved. Where necessary, an appropriate aliquot of the acid solution of the combined hydroxides can be taken to provide the proper quantity of beryllium for the determination. The volumetric procedure is capable of much better accuracy than tmhe photometric method. provided that the size of the sample is large enough to contain 0.1 to 0.2 gram of beryllium and that the aluminum content is known and small. This procedure is expediently used !&en the copper is first removed by electrodeposition. DETERMIYQTION OF BERYLLIUM CO\(:ESVTRATIOY I \ 4TMOSPIIERE
It ha5 been recogiiixed foi some time that elposuie to an atniosphere contaminated with heryllium 01 its compounds may, under certain conditions and in w a ~ not yet full! understood, give rise to health hazards (4, 7 , 1' 28, 41. 45, 56). Toxicologic reactions involving either the del nia 01 t l i r iespiratorv tract may occItr.
Determination of Beryllium Carbide in Beryllium Metal. This method is based upon the fact that beryllium carbide is attacked by hot 60% potassium hydroxide solution, liberating methane:
+ 4KOH
Be&
+ 2K2Be02
+ CHn
Simultaneously the beryllium metal is dissolved and hydrogen is evolved: Be
+ 2KOH
-+
K2BeOz
+ Hz
The evolved methane and Iiydrogeii can be osidized to ra14)ondioxide and water by passing over copper oxide wire (parked in n quartz tube) heated to 600" to 800" C:.
+ CUO -,CU + HzO ~ C + U 2H90 + COz CHI + 4CuO Hz
-+
All the water formed (6) can be removed by absorption in anh>.drous magnesium perchlorate. The carbon dioxide is then at)sorbed in Ascarite and weighed in the usual manner. Figure 5 shows the apparatus used. ANALYSIS OF ORES AND OXIDES OF BERYLLIUM
Ores of Beryllium (8, I O , 17, 19, 50). Following dissolution of the sample and volatilization of its silica content, the ammoniuni hydroxide group is precipitated, filtered, and redissolved in acid, If an average error of 3 ~ 5 %of the heryllium content present is acceptable, the colorimetric procedure is eniployed. The method is fairly rapid, specific, and applicable to rich or low grade ores alike. I n the case of low grade ores, however, excesses of aluminum and iron must be removed. Alternatively, the much lengthier gravimetric determinations by finally weighing as Iwyllium oxide or beryllium pyrophosphate are generallv ern-
EF G
=T
K LMNOP Figure 5 , Train Setup for Determination of Berylliuni Carbide hy Methane Evolution
k
A. l3O-ml. separatory funnel containing 100 rul. uf potassium 1iydi.oxide solution 8. 500-rnl. 3-necked borosilirate distillation flask C . Nitrogen inlet D . Water-cooled condenser E F . Bubblers containing concentrated sulfuric acid a: Mercury safety manometer H . Drying tower filled with Ascarite I . Fused quartz tube, 1.25 inches in outside diameter, 1 inch in inside diameter, 30 inches long, reduced end J . Lindberg Glo-bar combuation furnace K . Drying tower filled with anhydrous inagnesium perchlorate L. Drying tube filled with Drierite -11. Xesbitt weighing bulb packed with hsrarite and bottom layel of Drierite .V. Sesbitt counterpoise bulb, packed like iM 0 . Drying tube filled with anhydrous magnesium perchlorate P. Bubbler containing concentrated sulfuric acid
The analyst, as well as other workers handling products containing beryllium, should conduct all dust-, fume-, or vapor-producing operations in a well ventilated hood. Whenever excessive dusting or fuming is involved, the hood should be exhausted through proper equipment (electrostatic precipitator, filter, or scrubbing tower) to remove the beryllium froin the air. I n 1950 the United States Atomic Energy Commission reconimelded the following tentative maximum exposure levels ( 7 ): 2 y
V O L U M E 2 5 , NO, 11, N O V E M B E R 1 9 5 3 of brrylliuni pcr cubic meter aveiege conceutration throughout ail 8-hour day; 25 y per cubic meter in a single exposure; and 0.01 y per culiir meter average monthly concentration a t breathing zorie levels in outside surrounding areas.
To evaluate the degree of beryllium concentration in an atmosphere possibly contaminated with heryllium, a measured volume of air is drawn through a filter. The filter pad with the berylliumbearing dust or fume collected upon i t is analyzed for its beryllium content by spectrographic, fluorometric (&?), or photometric (41) mrthods following appropriate treatment to destroy the organic matter of the filter and to remove interfering quantities of other elements.
1585
Lundell, G. E. F., and Hoffnian, J. I., “Outlines of Methods of Cheniical Analysis,” pp. 94-3, New York, John Wiley & Sons, 1938. McClure, J. H., and Banks, C. T., U. S. Atomic Energy Commission, AECU-812 (November 1950). Margis, G. G., and Forbes. J. J.. Bur. Mines, Inform. Circ. 7574 (July 1950). Martell, A. E. and Plumb, 11. C., J . Phys. Chem., 56, 993-6 (1952).
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