Sur la thermogravimétrie des précipités analytiques: Dosage du chrome

By means of the CHEVENARD thermobalance, the precipitates used for the determination of chromium have been investigated and the following limits of temperature established:

     

2.

Determination of acidic dissociation constants of several vic-dioximes     

Charles V. Banks  Anton B. Carlson 《Analytica chimica acta》1952

The acidic dissociation constants of three vic-dioximes have been determined from spectrophotometric data. The results may be summarized as follows:

Precipitating reagent	Form in which weighed	Temperature limits
Ammonium hydroxide (to a chromic salt)	Cr2O3	> 812°
Ammonium hydroxide (to chromic acid)	Cr2O3	> 188°
Ammoniac (gas)	Cr(OH)3	440–475°
Ammoniac (gas)	Cr2O3	> 845°
Aniline	Cr2O3	> 830°
Hydroxylamine	Cr2O3	> 850°
Thiosemicarbazide	Cr2Oa3.H2O	380–410°
Thiosemicarbazide	Cr2O3	> 475°
Potassium cyanate	Cr2O3.H2O	320–370°
Potassium cyanate	Cr2O3	> 473°
Ammonium nitrite	Cr2O3	> 880°
Potassium iodo-iodate	Cr2O3	> 850°
Disodium phosphate	CrPO4	> 946°
Silver nitrate	Ag2CrO4	92–812°
Mercurous nitrate	Hg2CrO4	82–256°
Mercurous nitrate	Cr2O3	> 671°
Barium nitrate	BaCrO4	< 60°
Lead nitrate	PbCrO4	91–904°
8-Hydroxyquinoline	Cr(C9H6ON)3	70–156°
8-Hydroxyquinoline	Cr2O3	> 500°

     

3.

Spectroscopic investigations of hydrogen bonding interactions in the gas phase: Part VI. A microwave spectroscopie determination of geometry for the heterodimer (CH2)3O⋯HF formed between oxetane and hydrogen fluoride: hydrogen bonding as a probe for lone pairs     

A.S. Georgiou  A.C. Legon  D.J. Millen 《Journal of Molecular Structure》1980

The hydrogen-bonded heterodimer formed between oxetane and hydrogen fluoride is identified and characterised by means of its IR and microwave spectra. The following rotational constants (MHz) and centrifugal distortion constants (kHz) have been derived:

pK1	pK2
2,3-butanedionedioxime	10.6 ± 0.1	11.9 ± 0.3
1,2-cyclohexanedionedioxime	10.6 ± 0.2	12.4 ± 0.5
1,2-cycloheptanedionedioxime	10.7 ± 0.2	12.3 ± 0.5

     

4.

Polarographic determination of antimony in leadantimony alloys     

H.F. Hourigan  J.W. Robinson 《Analytica chimica acta》1954

A polarographic method for the determination of antimony in lead-antimony alloys has been developed. It was found that the interference due to the presence of varying concentrations of lead and hydrochloric acid would be eliminated by the addition of potassium chloride.

t001. The method gave satisfactory results within the range:

A	B	C	ΔJ	ΔJK
(CH2)O3?HF	9217	2575.1	2350.6	11.3	?57.0
(CH2)3O?DF	9157(ass)	2544.7	2329.3	9.9	?56

     

5.

Potentiometric study of silver(I)-thiosemicarbazonates     

M.Argüeso Jiménez  M.D.Luque de Castro  M. Valcárcel 《Microchemical Journal》1980,25(3):301-308

A potentiometric method is described for the determination of thiosemicarbazones involving the formation of a complex with Ag(I). This method is proposed for thiosemicarbazones of the following carbonyl compounds: salicylaldehyde, p-hydroxybenzaldehyde, benzaldehyde, picolinaldehyde, 6-methylpicolinaldehyde and p-dimethylaminebenzaldehyde. Stability constants of the complexes are determined by Ringbom and Harju's method.

FIG. 2. Variation of pAg + logα_{PAT (H)} + log ([Ag?PAT)]/[PAT])

2. Formation Constants of the Silver-Thiosemicarbazonates

Hydrochloric acid	4 — 8M
Lead	0 — 0.03M
Antimony	0 — 0.002M

     

6.

Sur la thermogravimétrie des précipités analytiques : Dosage du mercure     

Clément Duval  Nguyen Dat Xuong 《Analytica chimica acta》1951

With the help of the CHEVENARD thermobalance, the authors have traced the pyrolysis curves of the precipitates which are used for the gravimetric determination of mercury. The methods in which a period?ate, a molybdate, a vanadate, cupferron, and 2-chloro-7-methoxy-5-thiolacridine are used, have been rejected. Only four methods out of the 21 proposed for the precipitation of metallic mercury have been considered. The dissociation of mercuric nitrate has no interest from the analytical

Thiosemicarbazone	Log $\text{K}{}_{\mathrm{<mtext>f</mtext>}}$
-Benzaldehyde	15.5 ± 0.1
-Picolinaldehyde	14.0 ± 0.
-6-Methylpicolinaldehyde	14.5 ± 0.
-Salicylaldehyde	15.7 ± 0.1
-p-Hydroxybenzaldehyde	15.6 ± 0.
-p-Dimethylaminebenzaldehyde	17.2 ± 0.1

     

7.

Ion flotation of cadmium using ethylhexadecyldimethylammonium bromide     

Curtis McDonald  Shahram Taheri 《Microchemical Journal》1979,24(4):553-559

Cadmium ions react with the collector, ethylhexadecyldimethylammonium bromide (EHDABr), to form a surface-active sublate which can be removed from aqueous bromide

a. Effect of Foreign Metal Ions on the Flotation of Cadmium^a

Réactif précipitant	Forme de pesée	Limites de température
Electrolyse	Hg	<70°
Zinc + Iodure de potassium	Hg	<72°
Hydrazine	Hg	<55°
Acide hypophosphoreux	Hg	<71°
Acide nitrique	HgO	100°–200°
Acide chlorhydrique	Cl2Hg2	<130°
*Iodure de potassium	I2Hg	45°–88°
*Iodate de potassium	(IO3)2Hg2	<175°
Periodate de potassium	(IO3)2Hg2	<175°
Sulfure d'ammonium	SHg	<109°
*Thiosulfate de sodium	SHg	75–220°
Arséniate disodique	(AsO4)2Hg3	45–418°
*Thiocyanate de cobalt	[Hg(SCN)4]Co	50–200°
Thiocyanate de zinc	[Hg(SCN)4]Zn	<270°
*Chromate de potassium	CrO4Hg2	52–256°
Chromate de potassium ammoniacal	CrO4Hg2	52–256°
*Bichromate d 'ammonium + Pyridine	Cr2O7[Hg(C5H5N)2]	56–66°
*Sel de Reinecke	[Cr(CNS)4(NH3)2]2Hg	77–158°
Molybdate alcalin	[Cr(CNS)4(NH3)2]2Hg	77–158°
Tungstate alcalin	WO3	>880°
Vanadate alcalin	WO3	>880°
Iodure de cadmium ammoniacal	(HgI3)2[Cd(NH3)4]	<69°
Iodure de potassium + Sulfate de cuivre + Ethylène diamine	[HgI4][Cu En2]	à 20°
*Iodure de potassium + Sulfate de cuivre + Propylène diamine	[HgI4][Cu Pn2]	<157°
Acide oxalique	C2O4Hg2	<100°
Anthranilate de sodium	(C6H6O2N)2Hg	<113°
Pyridine	Cl2Hg(C5H5N)	<113°
Dithiane	Cl2Hg.C4H8S2	<97°
*Chlorure de cuivre-biguanide + iodure de potassium	[HgI4][Cu(C2N5H7)2]	60–175°
Cupferron	[HgI4][Cu(C2N5H7)2]	60–175°
*Thionalide	(C12H10ONS)2Hg	90–169°
Chloro-2 méthoxy-7 thiol-5 acridine	(C12H10ONS)2Hg	90–169°

Foreign ion	Foreign ion concentration (M) (×10?5)	Foreign ion removed (%)	Cadmium removed (%)
None			99.21
Zn2+	6.11	0.06	98.41
Cu2+	6.29	3.64	97.80
Pb2+	3.86	4.80	91.78
Cr6+	7.69	30.75	99.07 solutions by ion flotation. A typical ion flotation procedure involves passing air through a 250-ml solution containing 5 ppm Cd2+, 0.05 M Br?1, and 1.7 × l0?3M EHDABr at a flow rate of 40 ml/min for 1 hr. The procedure was simple and efficient. Chromium, copper, and zinc ions do not interfere under the experimental conditions.

a

Cd²⁺, 4.46 × 10^?5M; EHDABr, 4.25 × 10^?4; Br^?, 5 × 10^?2M; flow rate, 40 ml/min; time, 60 min.

     

Determination of acidic dissociation constants of several vic-dioximes

The acidic dissociation constants of three vic-dioximes have been determined from spectrophotometric data. The results may be summarized as follows:

Spectroscopic investigations of hydrogen bonding interactions in the gas phase: Part VI. A microwave spectroscopie determination of geometry for the heterodimer (CH2)3O⋯HF formed between oxetane and hydrogen fluoride: hydrogen bonding as a probe for lone pairs

The hydrogen-bonded heterodimer formed between oxetane and hydrogen fluoride is identified and characterised by means of its IR and microwave spectra. The following rotational constants (MHz) and centrifugal distortion constants (kHz) have been derived:

Polarographic determination of antimony in leadantimony alloys

A polarographic method for the determination of antimony in lead-antimony alloys has been developed. It was found that the interference due to the presence of varying concentrations of lead and hydrochloric acid would be eliminated by the addition of potassium chloride.

t001. The method gave satisfactory results within the range:

Potentiometric study of silver(I)-thiosemicarbazonates

A potentiometric method is described for the determination of thiosemicarbazones involving the formation of a complex with Ag(I). This method is proposed for thiosemicarbazones of the following carbonyl compounds: salicylaldehyde, p-hydroxybenzaldehyde, benzaldehyde, picolinaldehyde, 6-methylpicolinaldehyde and p-dimethylaminebenzaldehyde. Stability constants of the complexes are determined by Ringbom and Harju's method.

FIG. 2. Variation of pAg + logα_{PAT (H)} + log ([Ag?PAT)]/[PAT])

2. Formation Constants of the Silver-Thiosemicarbazonates

Sur la thermogravimétrie des précipités analytiques : Dosage du mercure

With the help of the CHEVENARD thermobalance, the authors have traced the pyrolysis curves of the precipitates which are used for the gravimetric determination of mercury. The methods in which a period?ate, a molybdate, a vanadate, cupferron, and 2-chloro-7-methoxy-5-thiolacridine are used, have been rejected. Only four methods out of the 21 proposed for the precipitation of metallic mercury have been considered. The dissociation of mercuric nitrate has no interest from the analytical

Ion flotation of cadmium using ethylhexadecyldimethylammonium bromide

Cadmium ions react with the collector, ethylhexadecyldimethylammonium bromide (EHDABr), to form a surface-active sublate which can be removed from aqueous bromide

a. Effect of Foreign Metal Ions on the Flotation of Cadmium^a

A new kinetic method for the determination of magnesium and its application to natural waters

A kinetic method is described for the determination of trace amounts of magnesium in the presence of calcium. The procedure is based on the inhibition of the manganese(II) catalyzed aerial oxidation of 1,4-dihydroxyphthalimide dithiosemicarbazone reaction by

2. Effect of Transition Metals^a

Transition metal	Concentration (M)	Percentage inhibition	Mg(II) found (×l05M)
Fe(II)	3.6.10?5	54.1	4.62
Fe(III)	3.6.10?5	47.8	4.48
Co(II)	3.4.10?5	50.0	4.53
Ni(II)	3.4.10?5	50.0	4.53
Cu(II)	3.1.10?5	52.0	4.56
Zn(II)	3.0.10?5	54.1	4.62
Cd(II)	1.7.10?5	52.0	4.56
Hg(II)	9.9.10?6	45.8	4.44
Sn(II)	2.1.10?6	50.0	4.52
Pb(II)	1.2.10?6	54.1	4.62

a

Conditions: 4.53.10^?5M Mg(II), 35 ng Mn ml^?1, 0.429 M ammonia, 1.6.10^?4M OH-PDT.

3. Determination of Magnesium in Natural Waters

			Mg(II) found (M)b
Natural water	Ca(II) presenta		Atomic absorption
sample	M	Kinetic absorption	method
Commercial	3.45 · 10?4	1.65 · 10?3	1.74 · 10?3
Commercial	5.46 · 10?4	1.57 · 10?4	1.81 · 10?4
Untreated	6.13 · 10?4	2.16 · 10?4	2.40 · 10?4
Treated	4.95 · 10?4	1.93 · 10?4	2.17 · 10?4

a

EDTA titration less the magnesium.

b

Average of three separate determinations. traces of magnesium(II). The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 594 nm. The calibration graph (percentage inhibition vs magnesium concentration) is linear in the range 329–535 · 10^?5M with an accuracy and precision of 1.2%. The method has been applied to the determination of magnesium in natural waters at low concentrations.

     

The vibrational ground state rotational spectroscopic constants and structure of the HCN dimer

Rotational spectra have been assigned for four isotopic species of the linear HCN dimer in the vibrational ground state. The spectroscopic constants are

     

10.

Spectrophotometric determination of sulfite with soluble mercury(II) compounds     

Ray E. Humphrey  George S. Ingram  Druce K. Crump 《Microchemical Journal》1982,27(3):351-356

Sulfite ion reacts with mercury(II) ion in acid solution to form the mercury(I) ion. The reaction is rapid and quantitative. The mercury(I) ion absorbs at 237 nm with a molar

5. Beer's law Data for Sulfite Complexes of Covalent Mercury(II) Compounds

isotope	-B0 (MHz)	DJ (kHz)	xN1 (MHz)	xN2 (MHz)
HC14N-HC14N	1745.80973(50)	2.133(30)	?4.0973(200)	?4.4400(190)
HC14N-HC15N	1700.30190(30)	1.939(40)	?4.1059(10)	-
HC15N-HC14N	1729.92082(20)	2.023(30)	-	?4.4339(6)
HC15N-HC15N	1684.28825(25)	1.900(30)	-	-

SO2 (ppm)	?HgCl2a	?HgBr2	?Hg(Ac)2b	?Hg(SCN)2
2.0	12,500	10,000	10,000	9,200
4.0	12,500	11,500	10,000	9,000
6.0	12,500	11,500	10,000	9,200
8.0	12,000	11,000	10,500	9,800

a

Molar absorptivity based on sulfite ion at 230 nm. Solution was 6.86 buffer.

b

Mercuric acetate solutions seemed to be somewhat unstable. absorptivity of about 25,000. The absorbance is linear over a range of approximately 0.5–5.0 ppm as SO₂. Covalent mercury(II) compounds form a complex with sulfite, Hg(SO₃)₂^2?, which absorbs at 230 nm and shows a linear response over a range of 1–8 ppm as SO₂.

     

Spectrophotometric determination of sulfite with soluble mercury(II) compounds

Sulfite ion reacts with mercury(II) ion in acid solution to form the mercury(I) ion. The reaction is rapid and quantitative. The mercury(I) ion absorbs at 237 nm with a molar

5. Beer's law Data for Sulfite Complexes of Covalent Mercury(II) Compounds

The mechanism and kinetics of energy transfer processes in the Xe–CCl4–M (M=CH4, C2H2, C2H4, C2H6 C3H6 and C3H8) mixtures irradiated by xenon resonance light

The mechanism and kinetics of energy transfer from Xe(6s[3/2]₁) resonance state (E=8.44 eV) to selected hydrocarbon molecules have been investigated by XeCl(B–X) (λ_max=308 nm) fluorescence intensity measurements at stationary conditions in Xe–CCl₄–M systems. Steady-state analysis of the fluorescence intensity dependence on the xenon and M pressure at constant CCl₄ concentration shows that these process occur in the two- and three-body reactions: Xe(6s[3/2]₁⁰)+M→products, Xe(6s[3/2]₁⁰+M+Xe→products. The two- and three-body rate constants for these reactions have been found (see Table 1Table 1. Experimental parameters of Eq. (8)found by least square method in Xe–CCl₄–C₂H₂ and Xe–CCl₄–C₂H₄ systems for chosen xenon pressures in the range 25–150 Torr. Linear correlation coefficients (R) are also shown     

12.

Performance of a new automatic carbon dioxide coulometer     

Edward W. D. Huffman  jr. 《Microchemical Journal》1977,22(4):567-573

The Coulometrics Inc. CO₂ coulometer has been shown to be an accurate and reliable CO₂ measuring device. The coulometric efficiency is essentially 100%. This means that the method can be considered as a standard reference method for CO₂. As with a CO₂ absorption tube, certain potential interferences must be considered, however, the removal of these interferences is well documented in the literature.The CO₂ coulometer has found a variety of applications in the author's

3. effect of flow rate on absorption of CO₂ by coulometer

Performance of a new automatic carbon dioxide coulometer

The Coulometrics Inc. CO₂ coulometer has been shown to be an accurate and reliable CO₂ measuring device. The coulometric efficiency is essentially 100%. This means that the method can be considered as a standard reference method for CO₂. As with a CO₂ absorption tube, certain potential interferences must be considered, however, the removal of these interferences is well documented in the literature.The CO₂ coulometer has found a variety of applications in the author's

3. effect of flow rate on absorption of CO₂ by coulometer

Amperometric titration of copper in brass

A direct amperometric titration of copper is described; o-(p-tolylsulfonamido) aniline serves as titrant. The optimum conditions are discussed and the method is applied to the analysis of copper in brass alloys.

t001. IV. Analysis of various samples in which copper was determined (Values given as percentages)

Enthalpies of combustion of 1,2-dihydroxybenzene and of six alkylsubstituted 1,2-dihydroxybenzenes

The standard (p^o = 101.325 kPa) molar enthalpies of combustion in oxygen at 298.15 K were measured by static-bomb calorimetry and the standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for 1,2-dihydroxybenzene (catechol) and six alkylsubstituted catechols:

Sur la thermogravimétrie des précipités analytiques: Dosage de l'uranium

A study has been made of the gravimetric methods for the determination of 4- and 6-valent uranium and two new forms of weighing are suggested, as oxalate and anhydrous oxmate. The following table summarizes the temperature limits, determined by means of the Chevenard thermobalance, for various precipitates:

Sur la thermogravimétrie des précipités analytiques : Dosage du gallium

With the help of the Chcvcnard thcrmobalancc the authors have determined the minimum temperatures necessary for quantitatively converting the derivatives of gallium into oxide Ga₂0₃.

Electrical conduction and diffusion studies in NH4H2PO4 and KH2PO4 single crystals

Electrical conduction (dc) studies are made with pure and cobalt(II)-doped single crystals of NH₄H₂PO₄ and KH₂PO₄. The effect of the dopant concentration on the enthalpy for the migration of protons and the enthalpy for the rotation of the H₂PO₄ group have been studied. It is suggested that proton migration occurs through a synchronous phosphate rotation mechanism. Tritium diffusion studies in KDP and ³²PO₄ diffusion in ADP crystals have been made. The mechanisms for the conduction and diffusion processes are found to be different in nature. The distribution coefficients of Co(II) dopant in ADP (2.92 × 10^?3) and KDP (1.14 × 10^?3) are calculated. The following enthalpy values are obtained.

Triene electrocyclizations: Some structure reactivity relations

Two stereoselective routes for the synthesis of trienes having a central cis double bond have been devised. These were employed for the synthesis of (Z)-1-(cyclohexen-1-yl)-1,3-butadiene (1), (Z,E)-1-(cyclohexen-1-yl)-1,3-pentadiene (2), (Z,Z)-1-(cyclohexen-1-yl)-1,3-pentadiene (3), 1,2-divinyleyclohexene (4), (E,Z)-1-phenyl-1,3,5-hexatriene (5), (Z,Z)-1-phenyl-1,3,5-hexatriene (6) and (E,Z)-1-(p-chlorophenyl)-1,3,5-hexatriene (7). Rates of the thermal electrocyclization and activation parameters were measured for these in inert solvents. The results are tabulated below.

Interelement effects in x-ray fluorescence spectrometry. Analysis of the iron-copper-sulfur system

The Rasberry-Heinrich and Claisse-Quintin equations give a good interpretation of the theoretical intensity-concentration relationship in x-ray fluorescence spectrometry. The influence constants (A_x, A_x) of these equations can be calculated. Trace element and structural effects require an empirical correction, which is important in iron-copper-sulfur systems (reverberatory mattes and copper concentrates). The empirical correction in combination with either of the above equations can furnish very good quantitative results from fluorescence intensity measurements.

t005. Analysis of some copper intermediates^a

Sur la thermogravimt́rie des prćipitś analytiques: Dosage de l'indium

The authors discuss several aspects of the chemistry of indium, giving evidence for a hydrate 2ln₂O₃.H₂O and studying in detail the behaviour of indium sulphide heated in air. Compared with that of gallium, the oxinate is particularly stable.Compounds used for the gravimetric determination of indium should be heated to the following temperatures in order to give correct results:

     

Hydroxide by ammonia	345°
Hydroxide by hexamethylene tetramine	546°
Hydroxide by cyanate	475°
Sulphide	94–221°, 320–544°, 690°
Phosphate	477°
Luteocobaltic indichloride	100–105°
Oxinate	100–285°
Diethyldithiocarbamate	100–210°