262 A. I~. MA.IUMDAI~ and 1~{. M. C~AKB, A BAB,TTY"

Ich fiihle reich verpflichtet, I{errn ProL Dr. Jo~A~ Pl~OSZT, dem Leiter des Institutes meinen aufrichtigsten Dank auch an dieser Stelle auszusprechen fi~r die Liebenswiirdigkeit, womit er racine Versuehe 'ermSglicht hat.

Literatur 1 BITSKEI, J. : Diese Z. 150, 268 (1956). - - ~ BITSI~EI, J., und .K. PETI~IC~t:

Magyar k6inikusok lapja: 14, 231 (1947).

J. BITsKEI, Budapest I., M&tray ut 6 (Ungarn)

Jadavpur University, Calcutta-32, India

Bismuthiol II as an Analytical Reagent Part I

Estimation of Bismuth

Von A. K. MAJUMDAR and M. M. CHAKRABARTTY

(Eingegangen am 3. Otctober 1956)

The reagent Bismuthiol I I (5-mercapto-3-phenyl-2-thiol-l,3,4-thio- diazole-2-one) was first prepared by Busch 1 and subjected to systematic study by DUBSK~ and his coworkers% The lat ter found the reagent to form characteristic coloured precipitates with a number of ions and to be highly suitable for the detection of small quantities of bismuth (identifi- cation limit is 1.2 #g and sensitivity is 1 par t in 28,000 parts). MA~tnvI- DAI~ 3 observed tha t the said reagent could be utilised for the gravimetric and the colorimetric estimation of bismuth with which the colour reaction was perceptible even at a dilution of 1 in 6,000,000 in presence of nitric acid and the colour system obeyed BEm~s law over a wide range of bis- muth concentration. From a 0.1 N nitric acid solution bismuth could be quanti tat ively precipitated as a stable complex which when dried at 105~ gave the composition as Bi(CsHsN2S3) ~ �9 1/2 H20. Further the reagent gave yellow precipitates with gold, mercury, silver, lead, platinum, arsenic and antimony, white with cadmium and zinc, brown with copper, brick red wi th tin and red with bismuth and palladium. In the same paper it was shown tha t zinc, cadmium, mercury, lead and palladium could be quanti tat ively precipitated like bismuth.

SE])IV]~C ~ utilised the reagent for the gravimetric estimation of mercury (ic). P~tNCHOUT and DUAL 5 during their thermogravimetric analysis of the bismuth precipitates found the method ~ by the Bismuthiol I I to be the best and recommended it for adoption.

As the method for gravimetric determination of bismuth by Bismu- thiol I I has been found to be satisfactory, the work has been extended

Bismuthiol II as an Analytical Reagent. I 263

to study the effect of acids for the complete precipitation of bismuth and its separation from other ions.

The potassium salt of the reagent gives with bismuth a highly crystalline, insoluble, easily washable, red coloured complex, which is stable in presence of acids but not in higher p~ regions and the complex maintains its composition from 40~ ~ C.

F r o m ac id solut ions b i smu th can be e s t ima ted in presence of F e 2+, A1, Cr, ra re ear ths , Ce ~+, Zr 4+, Ti ~+, U022+, Be, Mn, Th, Co, Ni, Mg, alkalis, alkMine ear ths , su lpha te , chloride and oxMate. I n presence of a c i t r a t e or a t a r t r a t e a t a pI~ be tween 1.5 and 2.5 i t can be s epa ra t ed f rom As s+, Ce ~+, MoO42- and W042 -. W h e n H g ~+, Pb , Pd , Cu, Ag, T11+ and Cd are p resen t t h e y are first p r e c i p i t a t e d a t a p~ be tween 6 and 8 in presence of a c i t r a t e or a t a r t r a t e . I-Ig, Pd , Cu and Ag are p r e c ip i t a t e d f rom a ho t solut ion, whereas Pb, T11+ a n d Cd from a cold solut ion as the complexes due to Pb, T11+ and Cd are soluble in ho t solut ion and b i smu th is t hen e s t i m a t e d in the i r acidif ied f i l t rates . Dur ing a s t u d y of the effect of p~, b i s m u t h is found to give a q u a n t i t a t i v e p rec ip i t a t e i n presence of a t a r t r a t e up to a m a x i m u m pH of 2.5 and the ac id i ty wi thou t t a r t r a t e can be increased up to 0.3 N in n i t r ic acid, 0.5 N in hydrochlor ic ac id and 1 N in sulphur ie acid. A t a p~ higher t h a n 2.5, b i smu th is no t comple te ly p r e c i p i t a t e d and remains in solut ion in presence of a t a r t r a t e , c i t r a te or eomplexone I I I .

I n presence of hydroch lor ic or su lphur ie ac id a t a p~ above 1 and in the absence of a t a r t r a t e , b i smu th chlor ide or su lpha te hydro lyses to give incorrec t resul ts . W i t h h igher acidi t ies t h a n the m a x i m u m l imi t men- t ioned above the r eagen t i tself decomposes wi th the sepa ra t ion of sulphur , spec ia l ly in presence of n i t r ic ac id and the so lub i l i ty of the b i smu th com- p lex as a rule increases wi th the ac id concent ra t ion .

Ions as F - and POa s- t h a t form insoluble compounds With b i smuth , Sb 3+ and Sn 2§ t h a t form less soluble compounds wi th the r eagen t and F e a+, V03- , Cr042-, As04 a- t h a t ac t as oxidis ing agents , interfere.

Experimental -Reagents and Apparatus. The reagent Bismuthiol I I was prepared as the potas-

sinm salt according to the method of BvseH 1 ~nd purified by recrystMlisation from alcohol as colourless needles. A 0.5% solution of the potassium salt of the reagent of m.p. 248 ~ C in water WaS prepared and used as precipitant. The reagen~ solution is to be prepared fresh and should be kept in amber-coloured bottle as there is slight and slow decomposition of the reagent on standing.

E. Merck's pure variety of bismuth sub-carbonate was dissolved in concentrated nitric acid and diluted with water to precipitate the bismuth as the sub-nitrate, which was again dissolved in nitric acid and made up to a definite volume. The bismuth content of the solution was determined by evaporating a known volume to dryness and igniting to oxide ~. The result was further checked by estimating bis- muth according to the method of MAJ~ID~R 3.

264 A. K. MAJVMD~ and M. M. CHAKRA.B2~I~TTY:

Standard solutions of other ions were prepared from chemicals of highest purity and the strengths of their solutions were determined by the standard procedures. I~are earth solution free from thorium was prepared from monazite sand and its strength was determined as mixed oxide (I~203).

p~ measurements were made with a bench model p~ meter.

Procedure E~timation oJ bismuth. An aliquot quantity of bismuth nitrate solution was

acidified with nitric, hydrochloric or sulphuric acid and diluted to 250 ml. The acidity of the solution might be adjusted up to a maximum of 0.3 N with respect to nitric acid, 0.5 N with respect to hydrochloric acid and 1 N with respect to sulphuric acid. To the diluted acidified solution of bismuth was added dropwise with stirring the reagent solution till there was no further precipitation. At high acid regions the point of complete precipitation could easily be judged as even a drop in excess of the reagent coagulated the precipitate, which then settled quickly. The precipitate was then filtered through a porous porcelain gooch or sintercd glass crucible, washed with hot water, dried at 105~176 and weighed. The bismuth content was found by multiplying the weight of bismuth complex with the factor 0.234 (see table 1).

Table I

Bi taken Nitric tIydrochloric Sulphuric Wt. of ppb. Bi found mg acid acid acid mg mg

54.69 10.94 10.94 10.94 14.42 14.42 14.42 14.42 14.42

0,1 N 0.01 N 0.3 N 0.5 N

0.1N 0.4 N 0.6 N

0.1N 1.0 N

233.4 46.8 46.6 44.4 61.6 61.6 62.0 61.8 62.2

54.61 10.95 10.90 10.39 14.37 14.37 14.51 14.46 14.55

W i t h hydrochloric or sulphuric acid, es t imat ion of b i smuth above p~ 1 was no t possible as the b i smuth chloride or sulphate hydrolysed. Nitr ic acid being an oxidising agent decomposed the excess reagent as the acidi ty of the solut ion was increased, specially when the solut ion was warmed before precipi tat ion. As the acidi ty was decreased to p~ 1 or above 1, there was no decomposi t ion of the excess reagent even on heating. A t lower acidi ty the solut ion should conta in abou t 2 g of ammo- n i u m n i t ra te to help the coagulat ion of the b i smuth complex.

Es t imat ion in Presence of other Ions

The same procedure as referred to above was followed and only in presence of cerous and ferrous ions the acidi ty of the solut ion was ad- jus ted wi th hydrochloric acid while in all other cases i t was adjus ted with ni tr ic acid and except oxalate in every other case the acidi ty was main- t a ined a t 0.1 N (see table 2) ; oxMate required a 0.2 N acidi ty to keep i t in solution.

Bismuthiol I I as an Analytical Reagent. I

Table 2

265

Bi t aken

mg

10.94 10.94 10.94 10.94 10.94 10.94 10.94 10.94 10.94 10.94 10.94 14.42 14.42 24.03

24.03 14.42 14.42

~ i 2+

C02-4-

l-V~n2+

A18+ The+ ~ r 3§

Ti4+ UO22+ R203 Be2+ Zr~+ (~e 3+ F e 2+

Ca2+

l~a 2+

Mg ~+ S r 2+

S04 ~- CI- C20~ 2-

Ions added

ing

107.80 106.40 203.00 162.00 238.00 216.30 229.20 217.80 122.00 109.90 94.60 32.00

308.00 120.00 120.00 120.00 120.00 500.00 300.00 280.00

W~. of ppt.

mg

46.6 47.0 46.8 47.0 47.0 47.2 47.2 47.2 46.8 46.8 46.8 62.0 61.4

103.2

103�9 61.4 61.6

B i ~ u n d

mg

10.94 11.00 10.95 11.00 11.00 11.04 11.04 11.04 10.95 10.95 10.95 14.51 14.37 24.15

24.16 14.37 14.37

E s t i m a t i o n in P r e s e n c e of T a r t r a t e or Citrate

Separation/tom Ce ~+, As 3+, MoO42- and WO~ 2- To the solution was added about 2 g of ammonium nitrate, 1 - 2 g of tartaric or

citric acid and neutralised with ammonia using methyl red indicator�9 The solution was then acidified with nitric acid and diluted to a volume of 250 ml. The p~ of the solution was maintained between 1.5 and 2.5. The reagent solution was then added dropwise with stirring till the bismuth was completely precipitated and the preci- pitate was allowed to settle and filtered. As the bismuth complex was found to be soluble in a hot solution of citrate or tar t rate it was washed first with cold water for a couple of times and then with hot water. I t was afterwards dried and weighed (see table 3).

Table 3

B i t a k e n

mg

14.42 14.42

14.42 14.42

14.42 14.42

14.42 14.42

Ions added

mg

CO + 80.0 �9 80.0

?r 2- 145.0 �9 290.0

WO~ 2- 133.8 �9 �9 200.7

As 3+ 15.00 . . 75.00

Wt. of ppt.

mg

60.6 61.4

61.4 61.8

61.8 61.4

61.4 62.8

Bi found

mg

14.18 14.37

14.37 14.46

14.46 14.37

14.37 14.69

P~

2.5 2.42

1.71 1.65

1.51 1.55

1.77 1.83

266 MAJU2IDiI~ and CHAKRABAI~TTY -" Bismuthiol. I I as an Analytical l~eagent. I

Separation/rein Hf+, pb2+, Cu2+, Ag+, Tl+, Cd2+ and Pd 2+

In this procedure the interfering ions were first precipitated in presence o fa ta r t ra te or a citrate, at a pa between 6 and 8, when bismuth remained in solution.

The solution was treated with 2 g of ammonium nitrate, 1--2 g of I~oehelle salt and neutralised with ammonia to yellow eolour ef the methyl red; i0~ of the solution was maintained between 6 and 8. This was then diluted, heated to boiling and to it was added the reagent solution till there was no further precipitation. The precipi- ta te so obtained was filtered through S & S fdter paper No. 589 and washed with hot water when T1 +, Cd ~+ and Pb e+ were absent. But in their presence, the solution was cooled after precipitation and washed with cold water as their complexes were found to have high solubility in hot solutions. The filtrate and washings were mixed together, concentrated to a volume of 250 m! and bismuth was precipitated accord- ing to the procedure mentioned above (see table 4).

Table 4

Bitaken

mg

19.22 14.42

19.22 14.42

19.22 14.42

9.61

19.22 14.42

19.22 14.42

19.22 14.42

Ions added

mg

Hg ~+ 21.84 .. 76.44

Pb ~+ 20.48 . . 153.45

Cu 2+ 20.68 . . 77.55

Pd ~§ 8.20

Ag + 20.00 .. 75.00

T1 + 20.71 . . 57.40

Cd ~+ 18.56 �9 69.60

Wt. of ppt.

mg

82.0 60.6

81.6 61.2

81.8 60.8

41,4

81.4 60.8

82.8 62.2

82.6 62.2

Bi found

mg

19.19 14.18

19.09 14.32

19.14 14.23

9.69

19.05 14.23

19.37 14.55

19.33 14.55

Summary The estimation of bismuth by the reagent Bismuthiol I I is studied

critically. The effect of acidity, reagent concentration and interfering ions are given in detail. The max imum acidity tha t may be tolerated for the complete precipitation of bismuth is 0.3 N in nitric acid, 0.5 N in hydrochloric acid and IN in sulphuric acid. Higher acidity than 0.1 N decomposes the reagent present in excess. In 0.1 N nitric acid bismuth has been separated from a number of ions like Ap+, Cra+, Th*+, rare earths, Z # +, TP +, U022+, Be ~+, Mn 2+, Co ~+, Ni 2+, Mg, alkalis and alkaline earths, SOt s-, Cl-, C20~ ~- and from Fe 2+ and Ce a+ in 0.1 N hydrochloric acid. In presence of a citrate or a ta r t ra te it can be separated from As 3+, Ce 4+, Mo04 ~- and WO~ 2- at plz 1.5 to 2.5. When I tg ~+, Pb 2+, Pd ~+, Cd 2+, Cu ~+, Ag + and T1 + are present they are first precipitated by the reagent at p~t 6 to 8

H. S ~ r Gewinnung schwermetall-, und sfliciumfreier Flu~s/~ure 267

in presence of a c i t r a te or a t r a t r a t e and the b i smu th is e s t ima ted gravi - met r ieMly in the acidif ied f i l t ra te . Ions as F - and PO4 3- t h a t form in- soluble compounds wi th b i smuth , Sb 3+ and Sn ~+ t h a t form less soluble compounds wi th the r eagen t and F e ~+, VO3-, CrO~ 2-, AsO4 3- t h a t ac t as oxidis ing agents , interfere.

References 1 Bvsc~, M.: Ber. dtsch, chem. Ges. 27, 2510 (1894). - - 2 Dv~s~s J. V., and

A. OKAS: Chem. Obzor 9, 171 (1934); Z. analyt. Chem. 96, 267 (1934). - - Dv~sK:~, J .V. , A. O ~ , ]3. O~A~ and J. T~TfLE~: Z. analyt. Chem. 98, 184 (1934). - - DUBSK~% J. V., A. O~A5 and J. T~T~LEK: Chem. Obzor 9, 173, 189 (1934); Mikro- chemic 17, 332 (1935); cf. Z. analyt. Chem. 107, 278 (1936). - - DVBSK~, J. V., and J. Ta~ILE~:: Chem. Obzor 9, 142, 203 (1934); Z. anMyt. Chem. 96, 412 (1934). - - 3 MAzv~II).~, A. K. : J. Indiun chem. Soc. 19, 396 (1942) ; 21,347 (1944). - - 4 M~L~I~, E. It., and F. wt~ D:fK~ C~csn~: J. Amer. chem. Soe. 27, 116 (1905). - - ~ P ~ . e~ov~, S., and C~. Dw~L: Anal. chim. Acta 5, 170 (1951). - -~ ~nD~wc, V. : Collect. ezechoslov, chem. Commun. 16, 398 (1951); cf. Z. anMyt. Chem. 137, 223 (1952/53).

A. K. M~zv~D~, Professor of Inorganic Chemistry, Jadavpur University, Jadavpur, Calcutta-32 (India)

Aus der Medizinischen Forschungsanstalt der Max-Planck- Gesellschaft, :Biochemische Abteilung, GSttingen

Gewinnung yon schwermetall- und silicium~reier Flulls~iure mit einer Poly~ithylenapparatur

Von HElgMA_NN STE GEMAN'N

M_it 3 Textabbfldungen

(Eingegangen am 8. Oktober 1956)

Sehr re ine w/il3rige Finorwassers toffs i /ure gewinn t m a n im Mlgemeinen d u t c h Des t i l l a t ion in P l a t i n a p p a r a t u r e n 3. Der unbes t r i t t enen QuMit/~t des Dest f l la ts s teh t der hohe Pre is der A p p a r a t u r gegenfiber.

I n den l e t z t en J a h r e n befM3ten wir uns m i t der M ik robe s t immung yon Si l ic ium un te r Zugabe yon ~'lul~s~ure zur Depo lymer i sa t ion gegebenen- falls vo rhandene r Polykiesels/~uren 2. Dazu ben6 t ig ten wir eine Flul3siture, die frei von Si l ic ium und aus anderen Grf inden frei yon Schwermeta l l en sein mul~te und ke inen R i i c k s t a n d geben durf te .

Schon 1952 wurde yon CoPPo~A u. I-IUGHES 1 eine A n o r d n u n g besehrie- ben, die als Gefs Po ly / / thy len (P.~) verwende t . Aber die Aus- beu te an Des t i l l a t i s t mi~i3ig und die S~ure is t zwar frei y o n Schwer- metMlen jedoeh n ich t frei yon Sflieium.

Zur Gewinnung re iner Flul3s~ure in e inem Arbe i t sgang benu tzen wir sei t l~ngerer Zei t eine A p p a r a t u r , die vo l lkommen aus handelsf ib l ichen