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Lipidomics has great potential for the discovery of biomarkers, elucidation of metabolic processes and identifying dysregulations in complex biological systems. Concerning biofluids like plasma or cerebrospinal fluid, several studies for the comparison of lipid extraction solvents have already been conducted. With respect to tissues, which can differ significantly in terms of dry matter content and composition, only few studies are available. The proper selection of an extraction method that covers the complexity and individuality of different tissues is challenging. The goal of this work was to provide a systematic overview on the potential of different extraction methods for a broad applicability. This study covers six different extraction procedures and four different reconstitution solvents applied to ten different porcine tissues. To get an overview of the individual lipid profiles, a workflow was developed for a fast and reliable tentative lipid annotation. Therefore, several machine learning tools were utilized, like the prediction of collision cross sections to support the tentative lipid identification in case of untargeted lipidomics. In terms of data evaluation, unsupervised (e.g. principal component analysis) and supervised (e.g. partial least square - discriminant analysis) methods were applied to visualize and subsequently interpret all generated information. Furthermore, the influence of the tissue composition on the extraction performance was investigated. It could be shown that the ten porcine tissues can be distinguished based on their lipid profile with the applied workflow and that the methyl-tert-butyl ether (MTBE) based extraction method (two-phase) showed the best overall performance for the 16 examined lipid species. With this method the highest number of features (428 in lung tissue) could be annotated. Upcoming one-phase extractions also showed a high potential concerning total number of extracted lipids. Methanol/MTBE/chloroform (MMC) extracted slightly less lipids (393 in lung and liver) than MTBE but turned out to be the best one-phase extraction method. Additionally, the numbers of extracted lipids obtained by isopropanol/water 90:10 (IPA90) (399 in stomach) and by isopropanol/methanol/chloroform (IMC) (395 in stomach) were similar to those of the modified Folch method (402 in stomach). One-phase extractions can therefore clearly be seen as preferable when a high throughput is needed., (Copyright © 2021. Published by Elsevier B.V.)

Amniotic fluid is the substantial factor in the development of an embryo and fetus due to the fact that water and solutes contained in it penetrate the fetal membranes in an hydrostatic and osmotic way as well as being swallowed by the fetus. Elemental composition of amniotic fluid influences the growth and health of the fetus, therefore, an analysis of amniotic fluid is important because the results would indicate abnormal levels of minerals or toxic elements. Inductively coupled plasma mass spectroscopy (ICP-MS) is often used for determination of trace and ultra-trace level elements in a wide range of matrices including biological samples because of its unique analytical capabilities. In the case of trace and ultra-trace level analysis detailed characteristics of analytical procedure as well as properties of the analytical result are particularly important. The purpose of this study was to develop a new analytical procedure for multielemental analysis of 18 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Mg, Mn, Ni, Pb, Sb, Se, Sr, U, V and Zn) in amniotic fluid samples using ICP-MS. Dynamic reaction cell (DRC) with two reaction gases, ammonia and oxygen, was involved in the experiment to eliminate spectral interferences. Detailed validation was conducted using 3 certified reference mterials (CRMs) and real amniotic fluid samples collected from patients. Repeatability for all analyzed analytes was found to range from 0.70% to 8.0% and for intermediate precision results varied from 1.3% to 15%. Trueness expressed as recovery ranged from 80% to 125%. Traceability was assured through the analyses of CRMs. Uncertainty of the results was also evaluated using single-laboratory validation approach. The obtained expanded uncertainty (U) results for CRMs, expressed as a percentage of the concentration of an analyte, were found to be between 8.3% for V and 45% for Cd. Standard uncertainty of the precision was found to have a greater influence on the combined standard uncertainty than on trueness factor., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Mycotoxin contamination is a common problem on feedstuffs, that can be formed on crops in the field, during harvest, storage, processing or feeding. The scope of the current study was to investigate the levels of Aflatoxin B1, Aflatoxin B2, Aflatoxin G1, Aflatoxin G2, Diacetoxyscirpenol, Ochratoxin A, Toxin HT-2, Toxin T-2 and zearalenone in a variety of feedstuffs (maize silage, alfalfa hay, cottonseed cake, corn grain and concentrates) fed to ruminants and the possible contamination of milk though consumption. For this purpose an easy and simple multiresidue LC-MS/MS method without any clean-up step was developed and successfully validated in feed and milk matrices. The LOQ of the method was set at 10 μg/kg for all analytes and 0.05 μg/kg for Aflatoxin M1 and Ochratoxin A in milk. The results showed that 7 cottonseed cake samples, out of 13 were contaminated with Aflatoxin B1 at a level higher than the maximum levels as set by EU Regulations and with Toxin T-2 with values ranging from 8 to 562 μg/kg. Nine maize silages and 6 alfalfa hay samples were contaminated with Aflatoxin G2 at levels higher than the maximum tolerance limit. No mycotoxins or their metabolites were found above the LOQ in any of the analyzed milk samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Derivative spectrophotometry (DS) was applied to determination of flavonols and a flavon in two-compound mixtures by means of 'zero-crossing' technique. Selected mixtures were, quercetin-kaempferol, quercetin-myricetin and quercetin-luteolin. The developed method was used as a complementary technique to a HPLC system, which does not separate quercetin and luteolin.

Chromatographic systems for the separation of amino acid mixtures on RP-18 as a stationary phase have been elaborated. The best results were obtained using methanol-water (1:1, v/v; 1:3, v/v; 1:5, v/v) as a mobile phase. The following amino acids have been examined: asparagine, arginine monohydrochloride, cystine, cysteine chloride, glycine, histidine monohydrochloride, hydroxyproline, isoleucine, leucine, lysine monochloride, methionine, ornithine monohydrochloride, phenylalanine, proline, threonine, tryptophan, tyrosine, serine, valine. Histidine (as monohydrochloride) and methionine were determined by first-, second- and third-derivative spectrophotometry in a mixture of several amino acids.

A new spectrophotometric method for determining titanium in vanadium-titanium ore with 2,2'-biquinoxalyl was developed. The analytical procedure to dissolve samples and separate titanium from vanadium and tin was elaborated as well. Furthermore, vanadium and iron were determined in the ore investigated.

UV spectra and absorption coefficients of biologically active copolymers of maleic anhydride with carbohydrates, terpenes and 1,3-dioxane derivatives were measured. The quantitative relationships of absorbance vs concentrations of polymers were determined as well. The possibility of determining the copolymer contamination due to monomers and oligomeric compounds was shown.

A new electroanalytical method for determining chloride ions with an Air-Gap cyanide sensor system is described. The method is based on the reaction of chloride with mercury(II) cyanide in dilute sulphuric acid. This reaction leads to hydrogen cyanide which can be determined with an Air-Gap cyanide sensor. Optimum concentrations of mercury(II) cyanide and sulphuric acid were established and an analytical curve was prepared for 1 x 10(-1)-1 x 10(-5)M Cl(-). The slope of the calibration curve was equal to 62.8 mV/log C. The correlation coefficient (R) was equal to 0.9992. The method can determine chloride with good results in high saline solutions and in the presence of surfactants, which is in contrast to direct potentiometry with a chloride electrode. The method was applied for chloride determination in fuses used for initiating explosions. The chlorides were determined both in the raw materials used to prepare the fuse braids and in the other fuse components. Chloride was also determined in drinking water and river water. In dependence of source, chloride amount analyzed in drinking water was in the range 2.18-182.6 mg/l. and 25.8 mg/l. in river water. A comparative analysis was carried out. In the first case, chloride was determined by a turbidimetric method, whereas in the second one by potentiometric titration against a chloride-ISE.

Volumetric and spectrophotometric methods for molybdenum determination based on reaction with 2,2'-biquinoxalyl (2,2'-BQx) in concentrated hydrochloric acid media have been developed. Absorption spectra of the 1,1'-dihydro 2,2'-biquinoxalylene complex shows the most intensive absorption band at 685 nm with molar absorptivity = 3.3 x 10(4) 1. mole(-1). cm(-1). The compound is characterized by good durability to high temperatures and concentrated acid media. The mentioned indicator gives distinct colour changes at the titration end-point. The spectrophotometric method for molybdenum determination is based on the use of the difference in absorbance between the oxidized and reduced forms of 2,2'-BQx. The indicator is reduced with Sn(II) and then part of it is reoxided as a result of addition of Mo(VI). The difference in absorbance between the blank determination and molybdenum sample increases linearily in the concentration range 0.2-2.0 mug Mo/cm(3). 2,2'-Biquinoxalyl was used as an indicator in the volumetric method for the determination of molybdenum concentrations in steel alloy. The interfering ions FE(III) and Cr(III) are easily eliminated as the precipitate of hydroxides. The mineral acids, hydrochloric sulphuric and perchloric acids, have been tested as reaction media.

The simultaneous determination of thallic and thallous ions, without preliminary separation, has been achieved by differential pulse anodic stripping voltammetry at a hanging mercury drop electrode. The electrochemical activity of thallic ions in 0.2M EDTA at pH 4.5 +/- 0.2 is inhibited by the addition of 0.01% poly(ethyleneglycol) of M.W. 20,000 (PEG 20,000). When the electrolyte also contains ascorbic acid at 0.01M concentration, the sum of thallic and thallous species can be determined.

Inductively coupled plasma spectrometry has been applied to the determination of La, Ce, Pr and Nd in alloy steels. Spectral interference by other alloying elements as well as by the lanthanides themselves was studied. The influence of other lanthanides on the Pr and Nd lines could be dealt with by correction equations. It was found that within the range of concentrations corresponding to mild alloy steel, at least one of the lines selected for determining the lanthanides was free from interferences. The detection limits for La, Ce, Pr and Nd in steel were 5 x 10(-5), 1.5 x 10(-4), 1 x 10(-4) and 2.4 x 10(-4)% respectively. The procedure was tested on standard samples and by the standard-addition method.

A thermal method of caesium determination is reported. The method is based on precipitation of Cs[Bi(SCN)(4)], thermal decomposition of this compound at 500 degrees , absorption of the evolved SO(2) in Na(2)HgCl(4) solution, and finally titration of the acid formed. The method can be used to determine caesium in the presence of potassium, ammonium and rubidium. When rubidium is present, caesium and rubidium can be determined simultaneously on the basis of the weight of the precipitate and the amount of sulphur dioxide evolved.

The influence of the following surfactants on the peak of copper in 0.2M EDTA at pH 4.5 was investigated: polyoxyethylated alkylphenols having an average of 3 and 9.5 ethylene oxide units; polyoxyethylene alcohols having 4 and 7 ethylene oxide units; poly(ethylene glycols) having M.W. 4000, 9000 and 20000; hexadecyltributylphosphonium bromide (HDTBPB), tetraphenylphosphonium bromide (TPPB),N,N,N,N,N',N',N-examethylhexamethylenediammonium bromide (HMB), benzyl(di-isobutylphenoxyethoxy) dimethylammonium chloride (Hyamine 1622), hexadecyltrimethylammonium bromide (HDTMAB), hexadecyldimethylbenzylammonium chloride (HDDMBAC) and tetrabutylammonium chloride (TBAC). HDDMBAC, as well as all the substances examined which contained an ethylene oxide chain, completely suppressed the copper peak. HDTBPB and TPPB partially suppressed the peak, whereas HDTMAB, HMB and Hyamine 1622 enhanced it. TBAC was without effect. In 0.2M EDTA at pH 4.5 containing TBAC at 0.01M concentration and 10 ppm of Rokafenol N-3, Cu(II), Pb(II) and Bi(III) can be tolerated at concentrations of up to 0.05M, the height of the thallium peak being unaffected. The precision of the determination (3-10%) and the recovery are satisfactory. A 10(3)-fold ratio of Fe(III) to Tl(I) does not interfere with the determination.

Conditions have been found which make possible the determination of copper in the presence of a large excess of bismuth by differential-pulse and anodic-stripping voltammetry without preliminary separation. The electrochemical activity of the bismuth, which usually interferes in the determination of copper, is inhibited by using tetrabutylammonium chloride (TBAC) as surfactant. In 0.2M EDTA and 0.01M ascorbic acid at pH 4.5 as supporting electrolyte without the surfactant present, trace levels of copper (1.5 x 10(-8)M) can be determined accurately if the molar ratio of bismuth to copper is not higher than 3, but if the electrolyte also contains TBAC at 0.01M concentration, bismuth can be tolerated in concentrations up to 10(-4)M, and the height of the copper peak is unaffected.

A gravimetric method based on precipitation of mercuric sulphide has been developed for determination of thiourea and some of its derivatives (acetylthiourea and sym-diphenylthiourea). Concentrated nitric acid is added to 0.1M mercuric nitrate, the solution is made alkaline with concentrated ammonia solution and thiourea (dissolved in concentrated ammonia solution), acetylthiourea (dissolved in methanol) or diphenylthiourea (dissolved in acetone) is added and the mixture is boiled. The precipitate is filtered off, washed, and dried at 110 degrees . The determination takes about 40 min. The method gives satisfactory results for thiourea and very good ones for diphenylthiourea and acetylthiourea.

On the occasion of Joseph Louis Gay-Lussac's 200th anniversary, after a short comprehensive review of his scientific activities and his life, his achievements in the field of analytical chemistry are discussed. Gay-Lussac extensively studied the reaction of hydrogen sulphide with different metals and consequently may be considered the founder of classical qualitative analysis. He developed titrimetry into a scientific method. He designed the first burette that became widespread in use. The terms burette and pipette were created by him. The combustion apparatus designed by him together with Thénard was the starting point for organic elemental carbon-hydrogen analysis.

Reliable standardization is a serious problem for most analytical methods. In spite of extensive work on interferences, the results are not suited for prediction of gross errors in any particular case. This paper is intended to show the power of sequential testing in practical atomic-absorption spectrometric analyses for the efficient detection of interferences causing changes in sensitivity; this test is carried out by comparing the sensitivity of the standard with the sensitivity for the sample, as determined by the difference between the signals for the spiked and unspiked samples. The simple computations can be carried out instantly and experimentation is terminated as soon as a conclusion can be drawn. The major advantage over the traditional tests lies in the smaller number of independent measurements, requiring less time and sample. Three separate cases are discussed: with the mean sensitivity of the standard known and the deviation expected to occur in one direction only (single-sided alternative hypothesis); with the standard deviation of the determination known and the deviation possibly occurring in both directions (double-sided alternative hypothesis); and with the mean and the standard deviation unknown but estimated during the test (sequential t-test). It is shown that assumptions about the normal distribution of the data do not impose serious restrictions in practical AAS work.

On the basis of light-absorption studies on solutions of Crystal Violet (CV) molybdogermanate in acetone, the optimal pH conditions for quantitative formation of molybdogermanic acid (MGA) have been determined. Di, tri-, and tetra-salts of MGA have been formed and isolated. It has been shown that formation of the higher salts is favoured by lowering the acidity, but this increases also the amount of the solid co-product CV-isopolymolybdate. To overcome this inconvenience the surplus molybdate ions are masked by adding oxalate ions, thus allowing the separation of the corresponding solid tetra-salt up to pH = 6.5; the molar absorptivity of this compound in acetone solution is very high (4.2 x 10(5) 1.mole(-1).cm(-1)).

The atomization of Sn from graphite surfaces is potentially hindered by reactions with the surface. The impregnation of graphite tubes with other carbide-forming elements (W, Zr, Ta, Mo) favourably alters the surface characteristics of the graphite furnace for the atomization of Sn. At the acid concentrations needed to prevent the hydrolysis of Sn, these surfaces are considerably more stable (even after more than 100 atomization cycles) than those of pyrolytic graphite. Two graphite furnaces of different design, the HGA 72 and the HGA 76, were tested. With impregnated graphite tubes the determination of Sn is possible in the HGA 72 with a detection limit of approximately 15 pg. In the HGA 76 the tin determination is vastly improved with respect to prolonged lifetime of the furnaces and stable signals over much longer periods of time. Detailed interference studies reveal that the use of the "gas stop" mode minimizes the influence of many ions that are frequently either introduced by the decomposition reagents or present in the sample itself. The practical potential of this method is demonstrated for the determination of Sn in a slag material and in copper- and aluminium-based alloys.

Ion-association complexes of permanganate with tetrabutylammonium can be dissolved in chloro- or bromobenzene and used for photometric titration of certain unsaturated hydrocarbons at 45-50 degrees . MnO(2) is precipitated and must be filtered off before the absorbance is measured.

The use of hydrogenated platinum electrodes allows observation of the electroreduction of some oxygenated ions, which is otherwise masked by the reduction of the hydrogen ion. The present paper deals with the reduction of molybdenum(VI) at a prehydrogenated platinum electrode in acid solutions. The experimental conditions for the electrode hydrogenation process are the following: 90 min at a cathodic current density of about 7 A/cm(2) for microelectrodes with an area of 0.02-0.03 cm(2); about 120 min at a current density of 1.5-2 A/cm(2) for microelectrodes with an area of 0.25-0.35 cm(2). The reduction of molybdenum(VI) in 0.8-1.6M H(2)SO(4) occurs in two consecutive steps: the more cathodic wave [Mo(V) to Mo(III)] is for the most part masked by the reduction of the solvent; the less cathodic wave [Mo(VI) to Mo(V)] takes place at E(1 2 ) values of about +0.07 V, is well shaped, diffusion-controlled and usable for the determination of molybdenum down to 4 x 10(-5)M or 6 x 10(-5)M if a rotating disk electrode is used. Interferences from diverse ions have been studied. A generalization of the effect of electrode hydrogenation on the reduction of those oxygenated ions so far studied [i.e., vanadium(IV), uranium(VI) and molybdenum(VI)] is presented.

The determination of trace levels of thallium in bismuth and bismuth salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent, in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte in the absence of surfactant, bismuth at concentrations below 10(-4)M does not interfere. When the electrolyte also contains tetrabutylammonium ions at 0.01 M concentration, bismuth can be tolerated at concentrations up 0.05M, and the height of the thallium peak is unaffected. It is thus possible to determine 1 nM Tl(I) in the presence of 0.05M Bi(III), i.e., Tl at the 1 x 10(-6)% level in bismuth. The precision of the determination and the recovery are satisfactory. Neither an 800-fold ratio of Cu(II) nor a 10(7)-fold ratio of Pb(II) to Tl(I) interferes in the determination. Other cations such as Zn(2+), Cd(2+), In(3+), Hg(2+), Fe(3+), Sb(3+) and Sn(4+) in 10(4)-fold molar ratio to Tl(I) have no effect on the determination. Thallium has been determined in bismuth metal and in bismuth nitrate of various degrees of purity.

The use of polyethylene glycols (PEG) of molecular weight from 200 to 15,000 for electrochemical masking has been investigated. A pH-4.4 tartrate buffer was found to be the most suitable supporting electrolyte, and 0.1% the optimum PEG concentration. PEGs of m.w. below 600 had little effect on the waves examined, and are useless for electrochemical masking. Under the conditions chosen, the waves of Bi(III), Sb(III) and In(III) are completely suppressed; the Cd(II) and Pb(II) waves are shifted to more negative potentials, and the Tl(I) wave is scarcely affected by PEGs. The Cu(II) wave behaves differently from the others. A method is proposed for the determination of lead and/or thallium in the presence of up to 5000-fold w/w ratios of bismuth, antimony or indium. The determination of both lead and thallium is only possible when the amounts are not too different, as the waves are quite close. Copper(II) interferes.

The molar absorptivities of the zirconium and hafnium Xylenol Orange (1:1) complexes are said to be similar in the acidity range 0.1-2.0M HCl. However, the absorbances obtained for the zirconium-Xylenol Orange complex in the acidity range 0.5-2.0M HCl are much higher than those for the same concentrations of hafnium. The absorbance differences are generally due to the higher stability of the zirconium complex at such acidities. Calculations based on the conditional stability constants of these complexes show the influence of dissociation on the results of simultaneous determination of zirconium and hafnium with Xylenol Orange.

Eight sensitive methods of spectrophotometric determination of thallium have been studied and compared experimentally. The comparative criteria were: molar absorptivity, colour contrast of the basic reaction, working concentration interval and practical determination limit for thallium, precision of the method (the standard deviation), and selectivity. According to these criteria the best methods of extraction-spectrophotometric determination of thallium are those using Brilliant Green, Crystal Violet, Methyl Violet and Rhodamine B. The sensitivity depends very much on the oxidant used for conversion of Tl(I) into Tl(III). The oxidants suitable for each of the recommended methods are discussed.

A gravimetric method based on precipitation of mercuric sulphide has been developed for determining thioacetamide and thioacetanilide. Concentrated nitric acid is added to 0.1M mercuric nitrate, the solution is made alkaline with concentrated ammonia solution, and thioacetamide (dissolved in water) or thioacetanilide (dissolved in alcohol) is added, and the mixture is boiled. The method has good accuracy, and takes about 40 min.

Two modifications of the spectrophotometric method for determination of the stability constants of ML and ML(2) complexes are derived and used for determination of the stability constants of Zr and Hf complexes with Methylthymol Blue. The dependence of the degree of dissociation of the complexes on the Zr and Hf concentrations is discussed.

Conditions have been found which make possible the determination of thallium and/or lead in cadmium and its salts without preliminary separation. The electrochemical activity of the cadmium, which usually interferes in the determination of thallium, is inhibited by the addition of 0.01% of polyethylene glycol of M.W. 4000. Thallium is determined by electrolysis at -0.74 V vs. SCE, in 0.1M EDTA solution: 10(-1)M thallium can be determined in the presence of 0.1M cadmium, while copper and lead at 10(-2)M and 10(-5)M respectively do not interfere. Lead is determined in 0.1M acetic acid containing 0.1% cetyltrimethylammonium bromide (CTAB). The addition of CTAB shifts the cadmium peak, as well as the optimum deposition potential for cadmium, to more negative values, making it possible to determine lead in the presence of cadmium as long as the deposition potential lies in the range between -0.50 and -0.56 V vs. SCE. Lead can be determined in the presence of ten times as much thallium.

The thermal stability of Cs [Bi(SCN)(4)] and Cs(2)Na [Bi(SCN)(6)] has been examined. The mechanism of the thermal decomposition of these compounds has been established. A simple procedure for analysis of the sinters has been developed and this procedure can be applied to other complex salts of bismuth.

The determination of trace levels of thallium in lead and lead salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte without surfactant, lead at concentrations below 0.5mM does not give a peak. When the electrolyte also contains tetrabutylammonium chloride (TBAC) at 0.01 M concentration, lead can be tolerated at concentrations up to 0.05M, while the height of the thallium peak is unaffected. It is thus possible to determine 5nM T1(I) in the presence of 0.05M Pb(II), i.e., Tl at the 1 x 10(-5)% level in lead. The precision of the determination (1-4%) and the recovery are satisfactory. Neither an 800-fold excess ratio of Cu(II) to Tl(I) nor a 10(7)-fold ratio of Bi(III) interferes in the determination. Thallium has been determined in a range of lead salts of various degrees of purity.

Under normal conditions, the reduction of uranium(VI) at a platinum electrode, in acid solutions, is masked by the reduction of the hydrogen ion. If the working electrode is subjected to hydrogen evolution (at a current density of about 7 A cm (2) for 90-120 min) the H(ads) on the platinum surface, acting as a bridge in the electron transfer, shifts the reduction wave of uranium(VI), in 1M sulphuric acid solutions, to potentials (E(1 2 ) congruent with - 0.03 V) less negative than that of the hydrogen discharge (about -0.25 V). The wave corresponding to the reduction of uranium(VI) to uranium(IV) is well shaped, diffusion-controlled, and can be used for the determination of uranium down to 2 x 10(-5)M or 3 x 10(-6)M if a rotating electrode is used. Interferences arise from those ions with similar E(1 2 ) [i.e., Cu(II) and Bi(III)], or from those such as permanganate and dichromate, which oxidize the H(ads) on the platinum electrode. Because of the time required for the electrode pretreatment, the determination is time-consuming but in some respects it appears a useful improvement over the DME.

Barium sulphate precipitates, formed by four different analytical methods, dried and ignited at different temperatures, have been examined with an electron microscope. The study of the dissolution of precipitates has been found useful for the investigation of thermal aging. On heating the precipitates, diffusion, which takes place at temperatures depending on structure, permits structural changes such as reordering to take place. Consequently, the structure of the ignited precipitates approaches the ideal arrangement.

Thirteen sodium salts have been investigated derivatographically. The weight change, rate of weight change and enthalpy change of the salts have been measured as a function of temperature. The temperatures at which the salts may be dried without decomposition are given. Some of the curves are explained in terms of the effects of heat and gaseous products on the structure of the salts.

Tungsten can be precipitated by a solution of Variamine Blue at pH 5. The precipitate is ignited to constant weight at a temperature above 600 degrees and weighed as tungsten trioxide. The method can be used for the determination of tungsten in alloy steels.

This review gives a survey of the theoretical considerations which led to the introduction of derivative methods in thennoanalysis, and of the development of complex thennoanalytical methods. The paper introduces the method of derivatography and its development, and surveys the wide field of its application in chemistry, technology, physical chemistry and biology.

The acid and base dissociation constants of luminol are determined at various ionic strengths. The transition interval occurs at pH 7.7-9.0, therefore luminol is a fluorescent indicator for the titration of strong and weak acids and strong bases. Its value as an indicator is established by titrating milk, red wine and cherry juice.

A device for the continuous introduction of powdered samples into spark and arc sources is described. The sample is pushed by a motor-driven spindle into the electrode gap through a tubular electrode. The method was found to be simple and versatile.

A method is given for the amperometric determination of thioacetamide (TAA) based on the reaction of TAA with copper(I) in ammoniacal solution. The reduction current due to the copper(I) is used to determine the end-point. The determination is carried out at constant temperature (25 degrees ), pH 8.0-9.8 (ammonia-urotropine buffer), and at constant potential (-0.6 V vs. S.C.E.), with a dropping mercury electrode as cathode and a saturated calomel electrode as anode. The solution is deaerated by a stream of electrolytically generated hydrogen. The titrations are carried out simply and rapidly and the results are fairly reproducible. The error is generally 1.0% for amounts of TAA ranging from 0.07 to 1.8 mg.

A rapid method is described for the simultaneous determination of 2,4-tolylene diamine and 2,4-tolylene diurea by infrared spectroscopy. The method is satisfactory for the diurea determination but gives rather large errors in the diamine determination.