3rd Ann&
Summer SymposZum
- Separations
Precipitation in Homogeneous Solution Separation and Determination of Barium, Strontium, and Calcium PHILIP J. ELVING AND ROBERT E. V.4N ATTA Purdrie University, Lufuyette, Znd., and The Pennsylvania State College. Stute College, Pa. Barium, strontium, and calcium can be quantitatively separated as readily filterable sulfate precipitates by digestion of an aqueous methanol solution containing dimethyl sulfate; the sulfate ion needed for precipitation is furnished by hydrolysis of the dimethyl sulfate. The coarseness and ease of filtration increase as the atomic weight of the alkaline earth metal decreases, both strontium and calcium. forming rather coarse precipitates. In the separation of barium in 2070 methanol, small amounts
of strontium interfere but large amounts of calcium do not; moderate amounts of sodium, potassium, and magnesium and large amounts of aluminum, ammonium, and iron do not interfere. Strontium and calcium are precipitated by modified procedures in higher concentrations of methanol; allowable amounts of sodium and potassium decrease as methanol concentration increases. Barium can be precisely determined In synthetic mixtures approximating the composition of barytes samples.
T
HE customary m'ethod of determining barium using relatively d i l ~ solutions e of barium and sulfate ( S , 5 ,a), wherein one reagent is added directly to the other at or near the boiling point, may involve several analytical errors, which fall (11) into three major categories: 1. Errors due to method of precipitation-e.g., a precipitate of barium sulfate formed by the addition of barium chloride solution to a hot sulfuric acid solution may contain considerable amounts of barium c,hloride. Even greater error is incurred when the precipitation is carried out in the reverse order (16). ,41though both barium chloride and sulfuric acid are absorbed and co recipitated with barium sulfate, the reagent present in excess wit be entrained to a greater extent. The amount of entrainment occurring is dependent upon the relat,ive concentrations of the reagents, rate and manner of mixing, and temperature. 2. Errors due t,o the presence of cations other than barium. Coprecipitation of alkali metals (18) and certain bivalent and trivalent ions may introduce errors. Coprecipitation of alkali metals occurs especially when sodium or potassium sulfate is used as precipitating agent. hmmonium may also be coprecipitated. Magnesium is only slightly entrained, while calcium may introduce rather large errors due to the slight solubility of calcium sulfate. Ferric ion is usually reduced to the ferrous state, which is entrained to a much lesser extent than the ferric iron or is removed by double precipitation with ammonium hydroxide with subsequent removal of the ammonium salts formed. Aluminuni is not greatly entrained, but high concentrations are best avoided. The effect of various cations is: K + > N a + > X H 4 + ; C a + + >> Mg++; F e + + + > AI+++ (10). 3. Errors due to the presence of anions other than sulfate. Coprecipitation of various anions with barium sulfate has been reported as increasing in two different orders: Fe(CN)a _-- < Fe(CN)s---- < I- < SCN- < C X - < Br- < Mn04- < C1- < C103- < NO2- < NO3- ( I S ) and CHICOO- < SCN- < I- < Br- < c1- < ClOn- < Fe(CN)$--- < &lnO4- < C103- < N O 3 - < Fe(CN)C---- < R r 0 3 - (10). Chromate cdprecipitat,es through the formation of mixed crystals with the barium sulfate (12). Phosphate is also entrained (14, 15). In most cases, entrainment errors due to the presence of anions may be decreased or eliminated bv precipitation a t or near the boiling point, followed by digestion of the precipitate over a steam bath. Because of the difficulty of securing accurate results in t,he precipitation of barium sulfate, investigators (17 , 23) have proposed empirical rorrection f:tctors to be applied to the weight of barium sulfate obtained. Quantitative results are ordinarily much more difficult to obtain in the precipitation of strontium, owing to the solubility of the sulfate formed. I n addition to the solubility error, determinn-
tion of strontium as the sulfate also includes the possibility of error due to entrainment effects similar to those encountered with barium. The dctermin:Ition of calcium :IS the sulfate has been discussed ( 1 ). The primary purpose of the present investigation was the development of a procedure for the determination of barium which would reduce or eliminate some of the errors mentioned and a t the same time produce a readily filterable precipitate; a procedure that would be suitable for the determination o f barium in the presence of large amounts of calcium was especially desired. A successful solution was found in the usc of the technique of precipitation in homogeneous solutions, whereby t,he alkaline rarth metal sulfate is precipitated in aqueous methanol solution by sulfuric acid formed on hydrolysis of dimethyl sulfate. The separation of strontium and of cdcium by the same technique was also investigated. The use of the technique of precipitation in homogeneous solution through generation of n prccipitating or neutralizing agent by hydrolysis has heen described by Willard, Gordon, Caley, and co-workers for magnesium ( 6 ) , calcium ( 2 , 1 9 ) , aluminum (dd), zirconium (21 ), and thorium ( 7 , 20). Caley and Elving (1 ) have described the precipitation of calcium as the sulfate in 90% methanol solution. Subsequent to the completion of the experimental work described in this paper, it was learned that Willard and Freund used the hydrolysis of sulfamic acid to generate sulfate ion for the separation of barium and calcium ( 4 ) . CHEMICALS AND SOLUTIONS
Standard solutions of barium and strontium ions were prepared by dissolving C.P. barium chloride dihydrate or strontium chloride hexahydrate in distilled water; standard calcium solutions were prepared by dissolving purified calcium carbonate ( 1 ) in hydrochloric acid. The exact voncentration of each solution was determined by evaporating a measured volume in a platinum dish with a slight excess of sulfuric acid, igniting to constant weight ih an electric muffle a t 750" C., and weighing the residual alkaline earth metal sulfate. Samples for the test analyses were prepared from accurately measured volumes of these standard solutions. For the study of the eutent of interference, accurately weighed amounts of the C.P. chlorides of the desired cations were dissolved in distilled water; acid solutions were prepared by diluting accurately measured volumes of the desired concentrated acids. Eastman Kodak practical grade (yellow label) or Fisher technical grade dimethyl sulfate was used in all experiments. No unusual difficulty was encountered in the use of dimethyl sulfate. The reagent was kept in a glass-stoppered bottle in a hood and was delivered into the sample solutions by means of a buret kept in the
1375
ANALYTICAL CHEMISTRY
1376 Table I.
Precipitation of Barium as Sulfate in 209'0 Methanol
Barium Taken, Mg. 1.0 5.0 10.0 30.1 65.2 100.3
Error, Mg. -0.1, -0.1 -0.2, 0.0 -0.1, +O.l 0.0,-0.1 -0.1, -0.2 0.0,-0.1
Table 11. Determination of Barium in Presence of Other Substances Added
Substance
Ma. 50.0 F e + + + 100.0F e + + + 100.0 Fa+++ 100.0F e + + + 500.0 F e + + + 500.0F e + + + 5.0 K: 50.0K 25.0 K: 100.0 K 5.0 N a + 50.0 N a + 25.0 Na: 100.0 N a + + + 500.0A1 5.0 M g + + 50.0 M g + + 10.0 M g + + 50.0 M g++++ 500.0Ca 500.0C a * * 25.0 C a + + 50.0C a + + 10.0 C a + + 10.0 C a + + 100.0C a + + 250.0C a + + 500.0C a + +
Added
Error
Barium
Error
Subntanoe
Barium
Ma.
Mu.
Ma.
Mu.
Mu.
10.0 10.0 10.1 100.3 100.0 100.3 10.0 10.0 100.3 100.3 10.0 10.0 100.0 100,3 100.3 10.0 10.0 100.0 100.0 1.0 5.0 10.0 10.0 100.0 100.3 100.0 100.0 100.0
+0.2
10.0S r + + 10.0S r + + I n% _.+ + 10.0 S r + + 10.0S r + + 1 .O SrZ+ 6.0S r + + 10.0 S r + + 10.0S r + + + 25.0 NH4 500.0NH4+ 50.0 "4: 100.0NH4 25.0 HCI 100.0HCl 50.0 HCI 500.0HCI 5.0 HNO: 10.0 HNOi 25.0HNOI 50.0 HNOi 100.0HNOi 10.O'HNOi 50.0 HNOi 100.0IINO, 50.0 HIPOI 100.0Hip04 250,OHip04 500,OHIP04
1.0 5.0 10.0 10.1 10.0 100.2 100.3 100.2 100.3 10.0 10.0 100.0 100.3 10.0 10.0 100.0 100.0 10.0 10.0 10.0 10.0 10.0 100.0 100.0 100.3 10.0 10.0 100.0 100,o
-0.1 +0.2 +0.2 +1.8
-1.2 -1.1 +0.3 -0.4 0.0 f0.2 +0.5 0.0 +0.5 -0.1 f0.1 0.0 f0.5 0.0
0.0 +0.4 +0.1 f0.4
-0.1 -0.1 +o. 1 f0.4
f0.3 0.0 -0.1 0.0 +0.8
+2.8
+0.1 +2.4 +3.0 +4.2
0.0 -0.1 -0.2 +0.5
+o.
1 -0.5 00 -0.5
0.0 -0.1 -0.6 -1.2 1 .? +0.1
-
+0.4
-0.1 0.0 -0.2 0.0 +0.2
hood. The usual grades of methanol were used. No unpleasant physiological effects were noticed from either the methanol or dimethyl sulfate. DETERMINATION OF BARIUM
Preliminary Experiments. The excess of dimethyl sulfate necessary for quantitative precipitation in a reasonable time w a determined by precipitating 100 mg. of barium with varying excesses of dimethyl sulfate in a 100-ml. solution containing 50 ml. of methanol. The dimethyl sulfate waa added in the cold and the eolutions were then allowed to digest on the steam bath until complete precipitation occurred. An excess of 75 to 1 (5 ml.) was picked as optimum on consideration of such factors as speed of precipitation, filterability, and ease of washing of the precipitate. I n a similar group of experiments, the barium was again precipitated by varying excesses of dimethyl sulfate, but one set of solutions was digested for 1 hour on the st,eam bath and a second similar set in a 50" C. water bath. Although both baths gave excellent results with a 75 to 1 excess, the steam-bath digestion required 15 to 20 minutes for complete precipitation, while the water-bath digcstion required a minimum of 4 hours. I n determining the optimum composition of medium, solutions containing 100 mg. of barium and a varying amount of methanol, ethanol, or %propanol were prepared, and the barium was precipitated with a 75 to 1 excess of dimethyl sulfate. The 20y0 methanol medium was found to produce quantitative results, as well as the most readily filterable precipitate. Although good results were obtained with ethanol and 2-propanol media, considerable creeping was encountered with the precipitates formed in these solutions. Effect of time of digestion was determined by preparing solutions containing 10 or 100 mg. of barium and 20 ml. of methanol in a total volume of 100 ml., and precipitating with a 75 to 1 excess of dimethyl sulfate, using digestion times of 15 to 60 minutes on the steam bath. Digestion times were considered as beginning with the appearance of heavy precipitation, which usually occurred 15 to 20 minutes after the solutions were mixed and placed on the steam bath. A digestion time of 60 minutes was picked as optimum, owin to ease of filtration of the precipitate formed. Procedure. h a n s f e r to a 250-ml. beaker the sample solution (75 ml. or less in volume) containing 1 to 100 mg. of barium preferabl present as the chloride or nitrate. Add 20 ml. of methanorand dilute to a total volume of 95 to 98 ml. Add to the
cold solution 0.5 ml. of dimethyl sulfate per 10 mg. of barium believed present (minimum volume to be added, 2 ml.) and immediately place the solution on the steam bath; the final volunie of the solution should be 100 ml. Allow the solution to digest on the bath for 75 minutes; if apprcciablc dccreasc in volumc occurs, add methanol to restore tho 100-ml. volumc. After digestion, filter through a weighed porcelain filtering crucible (Selas No. 3001). Wash the precipitate with 20% methanol, first by dccantation and then by stirring up the precipitate in the crucible with a stream of wash li uid. De ending upon the amount of barium present, 20 to 50.!n of washyiquid are required. Dry the crucible and contents for 15 minutes a t 100" to 150" C., thcn ignite in an electric muffle for 30 to 60 minutes at 750' C., cool in a desiccator, and weigh as barium sulfate. The thcorctic*al factor, BalBaSO, = 0.5885, is uscd to oalculutc rcsults. Separations. Using thc abovc proccdurc, satisfactory results wcre obtaincd for the determination ,of 1- t,o 100-mg. amounts of barium i n pure bttrium chloritic solutions (Table I). T o dctcrminc thc influcncc of other ions, pmcipit:ttions were madc in the prcscncc of known amounts of individual forctign cation8 and acids (Table 11). The results givcn arc typical of t,hoso obtaincd for thc particular foroign ion spoc:ificd; only limit,ing satisfitct,ory rosults arc givcn wit,h stress pl:iccd on sit,u:itions whcrc intcrforctnc-e may occur. Results obtained on cornpl(:x aynthctic samples i r e shown in T:tble 111; unfortunatvly, suitctblc sthndurd samples wcro not avctilitble. Ilowcvcr, the samplos of Table 111 hc~vostrontium to barium r d o s equal to or excectlirig those in the synthetic sctmples used by 1Gtllm:tnn (9) in tcsf,ing :I procctlurc for t.he tletcrmination of barium in harytcs. The oontcnt of tho other mctdlic constituents is higher; thc silica prcwnt in Kdlmann's smiplcs was omitted because it was removed in thc p r o liminary separations by the usual acid dehydration procwlure. Kallmann's mcthod for barium essentially involvcd fusion of the sample with potassium cut)onate, acid solution of thc samplc to convert all the clemcnts to t.lic chlorides, and sciparation-r,rdc:il)itation of the barium rn the chloride by the addition of oonc:c!nl,rrrtcd hydrochloric acid and n-butanol. The results ot)tainctl t)y the dimethyl sulfat,e procedure are comparablc in accuracy t.o those obtainwl by the morc difficult proccdurc dcscribcd by IGillmann, although the Iitttcr's procctlurc would hc morc n(lv:tnt,:tgcous in t.he prcscncc of appreciable amounI,s of strontium. DETERMINATION OF STRONTIUM
Preliminary Experiments. E:xpcrimcnt.s similar to those doscribed for barium rcvc:alotl that approxirnatcly a 60 l o l accws of dimothyl sulfate wus sufficient for tho qunntitativc prccipitation of stmntium, and that 70% mcthanol mcdium produced the bost rcwlt,s, ILS wc?ll as a rclativcly coarsc prccipitiitc which w u rctadily filtcrath. Cnrcfd policing of tf!c prwipittLtion bertkcrs was I'ound necessary twc:ausc of tho ttmdcncy of II film of st,rontium sulfate to :ttlhcrc to t h o ghws wr~lls. Neccssury conditions of digcstion wcrc detcrmincd by prcparinpl solutions containing varying amounts of gtroiitium and 70 ml. of methanol in a t,otal volume of 100 ml., and prccaipitating with a 50 to 1 CXCCHS of dimethyl sulfate, using digestion tirncs of 45 to 60 miriutw on the steam hath followed tiy 0 to 30 minuted standing a t room tcmpcraturc. A digestion timc of 1 hour on the stcrtm bath plus 1,5 minutes' staritling a t room tcrnporaturc wim pic:kcd as optimum, owing to tho case of filtration and handling of the precipitatcs thus digcstcd. Procedure. Transfar to a 250-ml. bc:rkcr the sumpl(b solution (25 rnl. or lcss in volunic) contrhining not, n i o r c th:m 126 ing. of :LS thc chlorido or n i h t c . Add 70 strontium prcfcrabl ml. of mcthanol anYfreSent ilutc with watcr tm :L tntid volurno of 96 to 98 ml. Add t,o the cold solution 0.5 ml. of t1irnc:t~hylnulfatc: for each 10 mg. of strontium (2 rnl. minirnum) ; i r i t l irnmct1i:~lc:lyplace t,hc solution on the stcam bath; :itltl mcth:Liiol 11s may tw nc(:(:sm r y to maintain the volurnc: at I00 ml. Ilcrno,vc nftw 1 hour on thc hnth and allow to Rtmd ut, room t,c:mpr:r:tt,urc!for 16 rninutcs. Filter through a weighed porcelain filtering crucible (Solua No, 3001). Wash the prcc:ipitat,c with 70% methanol, first by clecrtntation and then by stirring up the precipitate in thc c:ruc~it)lewith a stream of wash liquid. Dc ending upon the amount of strontium present, IO to 30 ml. of wasR liquid arc required Dry thc c r u c i ~ e and its contents for 15 minutes at 100" to 150' C., then ignite in an
V O L U M E 2 2 , N O . 11, N O V E M B E R 1 9 5 0
i3n which as previously reported ( I ) was found to be necessary for the quantitative precipitation of calcium. Suitable studies revealed that optimum results were obtained by a two-stage digestion in which and the of the precipitation were carried out in 40 or 50% methanol solution containirrg a large amount of dimethyl during 30 minutes' digestion on the bath and (2) the to 90% methanol was t,hen allowed to
Table 111. Determination of Barium in Synthetic Mixtures Cornposition
A1+++
~ e + + +
Sample, M g .
10.0 10.0 10.0 10.0 10.0 10.0 3.0 100.3
50.0 50.0 100.0 100.0 100.0 100.0 1.0 92.6
1 0 0 . 1 102.3 100.0 102.4
101.8 101.7
Ba 93.4 93.3
+O.l
+1.5 +1.4
50.0 50.0 100.0 100.0 100.0 100.0
10.0
16b:o
E;++++ Ea*++ Sr++ Ba++
50.0 50.0 100.0 100.0 100.0 100.0 5.0 100.3
50.0 50.0 100.0 100.0 100.0 100.0
...
+
9.8 9.9
20.0 20.0 50.0 50.0 50.0 50.0 5.0 49.2
50.0 50.0 50.0 50.0 3.0 49.2
Found, Mg. 101.1 49.8 ,100.9 49.7
49.0 49.2
20.0 20.0 50.0 50.0 50.0 50.0 1.0 100.3 +
Ba + Error, M g . +0.8 f0.8 + 0 . 6 +0.7 +0.6 +0,5
20.0 20.0
20.0 20.0
50.0 20.0 100.0 100.0 100.0 100.0 5.0 10.1
50.0 50.0 50 0 50.0 1 o 56.4
46.6
10.3 10.1
46,5
50.0
50.0
100.0
100.0 100.0 250.0 10.0 10.1 10.4 10.5
+
-0.2 -0.1
+2.0 0.0 +2.1
-0.2 0.0
electric muffle for 30 to 60 minutes a t 750" C., cool in a desiccator, and weigh as the sulfate. The theoretical factor, Sr/SrSOI = 0.4771, is used to calculate. results. Separations. The procedure described was used for determining strontium in pure strontium chloride solutions; satisfactory results were obtained in the range of 5 to 125 mg. of strontium (Table IV). To determine the influence of other ions, determinations were made in the presence of known amounts of foreign ions, typiral results indicative of the extent of interference are given in Table V; the limitation on the data in this table is the same as indicated for Table 11. Results obtained on complex synthetic samples are shown in Table VI. DETERMINATION O F CALCIUM
Preliminary Experiments. Experiments on calcium similar to those described for barium and strontium indicated that a radically modified procedure was necessary because of the very ?low rate of hydrolysis of the dimethyl sulfate in the 90% methanol,
Table IV.
Precipitation of Strontium as Sulfate in 70% Methanol
Strontium Taken, M g . 1 .o 2.5 4.9 10.0 12.9 13.2 29.9 65.0 99.8 125.8 126.5
Error, M g . -0.2, -0.3 -0.3, -0.2 0.0,-0.2 -0.1, -0.1 -0.2 0.0 -0.2, -0.1 0.0,-0.2 0.0,f0.1 0.0 0.0
stand at room temperature for 6o minutes. Because 20-mg. amounts of calcium gave only a slight precipitate under such conditions, results are not reported for amounts of calcium less tllan 50 nig.; i$rith small amounts of calcium (20 mg. or less) the procctlure would essentially duplicate that of Caley and Elving (1 ).
f0.2
1-0.2 ,+0.3 0.0 +0.4
+0.1
Procedure. Transfer to a 250-ml. beaker the sample solution (10 ml. in volume) co'ntaining 50 to 100 mg. of calcium preferably present as the chloride. Add 17 to 25 ml. of methanol and 15 ml. of dimethyl sulfate. Digest on a steam bath for 30 minutes, remove, dilute to 100 ml. with methanol, and allow to stand a t room temperature for 60 minutes, then filter through a weighed porcelain filtering crucible. Wash the precipitate with 90% methanol, first by decantation and then by stirring up the precipitate in the crucible with a stream of wash liquid. Depending upon the amount of calcium present, 20 to 50 ml. of wash liquid are required. Dry the crucible and contents for 30 minutes a t 100" t o 1.50" C., then ignite in an electric muffle for 30 to 60 minutes a t 750" C., cool in a desiccator, and weigh as calcium sulfate. The theoretical factor, Ca/CaS04 = 0.2944, is used to calculate results. Separations. The procedure indicated was used for the determination of calcium in pure calcium chlxide solutions, and in solutions containing individual foreign ions (Table VII). Results obtained on synthetic mixtures are given in Table VIII. No extensive experiments were performed on the separation of calcium by precipitation in homogeneous solution and on possible interferences with the method, because the precipitation and
Composit i o n . % A l + + + 100.0 F e + + + 100.0 100.0 hfg: 100.0 Na 100.0
Added
Substance
M Q.
30.0 F e + + + 100.0 F e + + + 100.0 F e + + + 250.0 F e + + + 1.0 C a + + 5.0 C a + + 5.0 C a + + 5.0 C a + + 1.0 C a + + 5.0 C a + + 5.0C a + + 5.0 C a + + 1 .O Cat++++ 50.0A1 125.0 A I + + + 25.0 A I + ' + 75.0 A I + + + 125,0Al+++ 250.0 AI+++ 125.0A I + + + 25.0 M g + + 25.0 M g + + 10.0 M g + + 25.0 M g + +
Determination of Strontium in Presence of Other Substances Strontium Mg.
12.7 12.7 125.7 125.7 1.0 1.0 0.9 4.9 9.9 9.6 96.2 99:2 99.2 12.8 25.5 64.3 64.7 64.3 64.3 126.5 4.9 9.9 12.7 12.7
Error
MQ. 0.0 +0.2 +0.4 +0.5 -0.2 -0.1 4-0.4 +o 2 +n 1 +o 7 f0.7 +o 8 f0.5
-0.4 -1.0 -0.1 -0.5 -0.3 +0.3 -0.2 -0.4 -0.6 f0.2 -0.3
Added
Substance M9. 25.0 M g + + 75.0 M g + + 125.0 M g + + 250.0 M g + + 250.0 M g + + 250.0 M g + + 250.0 Mg+++ 10.0 Na 100.0 N a + 100.0 N a + 100.0 K a + 150.0 N a + 100.0 h-'Bc+ 10.0 K 25.0 K + 50.0 K: 100.0 K 250.0 K + 10.0 "4: 25.0 NH4 50.0 NH,+ 100.0 NH4+ 250.0 NR,+
Strontium
Error
Mg.
Mg.
99.2 63.6 63.6 63.6 49.4 99.2 125.7 12.7 12.8 25.5 64.3 64.3 525.7 12.7 12.7 63.6 125.7 125.7 9.6 9.6 96.2 96.2 96.2
+O. 1 -0.6 -0.1 -0.9 -0.8 -0.6 -0.9 +0.1 +0.3 +0.2 +0.2 +0.5 +0.5
+0.2 +0.1 +0.2 +0.5 f0.6
+O.l +0.2 +0.3 4-0.4 +0.7
Sample, M g . B 50.0 50.0 50.0 50.0 50.0
C
10.0 10.0 5.0 25.0 25.0
D
E 20.0 10.0 25.0 20.0 20.0 2.0 95.6
F G 20.0 20.0 30.0 30.0 25.0 50.0 50.0 50.0 50.0 50.0 *5.0 5.0 20.4 23.9
126:5 64.7
13 2
20.0 30.0 25.0 50.0 50.0 2.0 20.4
126.2 64.8 126.3 64.9
13.2 13.3
S r + +Found, Mg. 20.4 95.6 20.6 20.3 95.8 20.5
+
Table V.
Determination of Strontium in Synthetic Mixtures
Table VI.
...
-
Sr Error, M g . 0.0 0.0 0.0 + 0 . 2 f0.l -0.1 +0.2 +0.1
23.4 23.7
I 20.0 20.0 25.0 20.0 20.0 5.0 95.6
47.0 96.8 46.7 97.1
+ +
-0.3 +O.l -0.2 f0.2
Table VII.
...
H 20.0 20.0 25.0 20.0 20.0 5.0 46.2
-0.5 -0.2
+0.8
+1.2 +0.5 +1.5
Determination of Calcium in Concentrated Methanol Solution
.%dded Substance, M g .
,.....
...... 500.0M g + + 200.0 M g + + 5.0 Na: 2.0 Na 5.0 K + 2.0 K +
Calcium, M g . 50.7 104.2 104.2 104.2 104.2 104.2 104.2 104.2
Error, M g . - 0 . 2 , -0.3 0.0, 0.0 +0.4 f0.2 4-0.8 +0.3 4-0.4 +o. 1
ANALYTICAL CHEMISTRY
1378
Ni
.
2.0 2.0 104,2
+
K
CB'+
A(:KNOF.' L E I W M E N T (:a++
found, mg.
Ca +
error, nig.
+
104.R 104.4
+0.3 fO.2
104. n 104.4
fn.1
+o
2
I'lit- i i r i t h o r n would lilw to rtcknowlotlge tho aid of Burburu Snoki! with wino of t>hocxpcriinental work anti the aid of t,hc! Itont~iirc!h Corporat~ion,which furnishctl a Frederick Critrtlnc*r ( h r t I r141 grunt. iilion which a o m ~of t t i v work dwwril)(!d w w done.
