ORGANIC REAGENTS FOR PLATINUM METALS: II. THE GRAVIMETRIC DETERMINATION OF RHODIUM

1949 ◽  
Vol 27b (2) ◽  
pp. 72-75 ◽  
Author(s):  
R. L. Haines ◽  
D. E. Ryan
Keyword(s):  
Acetic Acid ◽  
Nitric Acid ◽  
Organic Compounds ◽  
Atomic Weight ◽  
Similar Type ◽  
Platinum Metals ◽  
Organic Reagents ◽  
Molecular Weights ◽  
Gravimetric Determination

Rhodium may be precipitated quantitatively with 2-mercaptobenzoxazole or 2-mercaptobenzothiazole. An acetic acid precipitating medium is preferred; slight variations in the concentration of acid, when nitric acid was used, caused low results. Several similar type organic compounds showed no advantages over the above two. The complex appears to have three molecular weights of the reagent combined with one atomic weight of rhodium.

Rapid Gravimetric Determination of Mercury in Organic Compounds

1956 ◽  
Vol 28 (3) ◽  
pp. 406-407 ◽  
Author(s):  
H. F. Walton ◽  
H. A. Smith
Keyword(s):  
Organic Compounds ◽  
Gravimetric Determination

Thin Layer Densitometric Determination of Rotenone and Deguelin

1969 ◽  
Vol 52 (1) ◽  
pp. 182-187
Author(s):  
Norman E Delfel ◽  
William H Tallent
Keyword(s):  
Acetic Acid ◽  
Standard Deviation ◽  
Nitric Acid ◽  
Thin Layer ◽  
Solvent System ◽  
Ammonia Vapor ◽  
Acid Vapor ◽  
Tephrosia Vogelii ◽  
Infrared Methods

Abstract Rutenone and deguelin are separated by chromatography on silver nitrate-impregnated silica gel G with chloroform acetone: acetic acid (196:3:1) solvent system. Glass plates, 20 × 20 cm, are coated with a special spreader producing a 0.25 mm layer and a 1.00 mm band at the upper end. Since additional solvent is required to saturate the thicker band, such plates give resolutions comparable to plates twice as long. Developed plates are treated with nitric acid vapor, then ammonia vapor, to produce dark spots for the rotenoids. Plates are scanned with a commercial densitometer, and the quantity of rotenoids is calculated from peak area in the resultant curve. Kecoveries of rotenone and deguelin added to extracts of Tephrosia vogelii, Lonchocarpus nicou, and Derris elliptica averaged 104.1 and 99.4%, respectively. The standard deviation of the method applied to plant extracts was 7.9% for rotenone and 8.3% for deguelin. The amounts of rotenone in the L. nicou samples were comparable to those determined by the AOAC crystallization and infrared methods.

Determination of activity coefficients of aqueous solutions of urea in the ultracentrifuge

1970 ◽  
Vol 23 (5) ◽  
pp. 915
Author(s):  
EF Woods
Keyword(s):  
Aqueous Solutions ◽  
Activity Coefficients ◽  
Similar Type ◽  
Point Of View ◽  
Published Data ◽  
Molecular Weights ◽  
Equilibrium Sedimentation ◽  
Aqueous Urea ◽  
Determination Of Activity

Apparent molecular weights of aqueous urea solutions have been determined by equilibrium sedimentation over the concentration range 1-9M. At the speeds used in the ultracentrifuge (39460 to 67770 r.p.m.) there was evidence of the effect of pressure on the sedimentation of urea. Apparent molecular weights of urea were therefore calculated at the solution-air meniscus where the solution is at l atm. The derived activity coefficients showed a similar type of oncentration dependence to published data for urea but there were significant quantitative differences. The significance of the results from the point of view of calculating theoretical distributions in the ultracentrifuge is discussed.

scholarly journals XI. On the molecular weights of the substituted ammonias. No. I. Triethylamine

1883 ◽  
Vol 35 (224-226) ◽  
pp. 347-349
Keyword(s):  
Molecular Weight ◽  
Atomic Weight ◽  
Tertiary Amines ◽  
Hydrogen Atoms ◽  
Whole Numbers ◽  
Molecular Weights ◽  
Dry Distillation ◽  
Pure Substances ◽  
Ammonium Compounds

The conduct of the experiments relating to a new determination of the atomic weight of manganese recently communicated to the Society has led us to prosecute some further studies in this field of research. The following note deals with the preliminary results arrived at regarding the molecular weight of a member of a class of bodies which, strange to say, have not been previously selected for accurate determinations of this kind. The substituted ammonias are peculiarly fitted to reveal the effect of small differences from whole numbers in the conjoint values of the atomic weights of carbon and hydrogen. By selecting tertiary amines of high molecular weight it is possible to integrate these small positive or negative increments through the increase in the number of carbon and hydrogen atoms in the substituting radical. There is also a special advantage in employing the fully saturated ammonium derivatives for experiment. Theoretically it ought to be possible to ascertain by this method whether the atomic weight of hydrogen differs from unity, provided the atomic weight of carbon be accepted as sufficiently well defined, from other methods of investigation. The difficulty of getting perfectly pure substances for such work, together with the hygroscopic character of the ammonium compounds, introduces serious difficulties, and for the purpose of testing the accuracy of the proposed method, the preliminary experiments have been made with triethylamine. The triethylamine employed was made by the action of chloride of ethyl on ammonia, and was transformed into the bromide of tetraethyl-ammonium. This bromide of the fully substituted ammonium was decomposed by dry distillation into triethylamine and bromide of ethyl, and the base separated in the form of the chloride. The free base was separated from the chloride with caustic potash, and after careful drying with anhydrous oxide of potassium was subjected to fractional distillation. The portion boiling between 90° and 91° was converted into the hydrobromate and its equivalent relation to silver determined, after the method of Stas, with the following results:— Weight of salt Weight of salt Molecular weight of in vacuo. in vacuo. (C 2 H 5 ) 3 N.H Br. 6·6248 ...... 3·9219 ....... 182·313 8·24088 ...... 4·8798 ....... 182·270

THE DETERMINATION OF THE METALS OF THE PLATINUM GROUP IN NICKEL ORES AND CONCENTRATES

1940 ◽  
Vol 18b (11) ◽  
pp. 333-344 ◽  
Author(s):  
F. E. Lathe
Keyword(s):  
Nitric Acid ◽  
Reliable Method ◽  
Similar Material ◽  
Platinum Metals ◽  
General Application ◽  
Substantial Modification ◽  
Method Of Determination ◽  
Sulphide Ores ◽  
Nickel Ores

Most published methods for the determination of platinum and associated metals are not of general application to ores and concentrates, and their accuracy as applied to unknown material is in many cases seriously open to question. The methods here described are chiefly based upon experience with the products of the Sudbury area, but are believed to be applicable without substantial modification to all sulphide ores of nickel and to smelter and refinery products derived therefrom. Methods of concentrating the platinum metals are described, an outline is given of an approximate method of determination based on sulphuric acid parting, and details of a more reliable method in which nitric acid is the parting medium are set out. The results obtained are compared with those of Beamish and associates on similar material.

scholarly journals The determination of atomic weights by means of the microbalance, and the values obtained for carbon, nitrogen, and fluorine

1936 ◽  
Vol 236 (760) ◽  
pp. 77-102 ◽  
Keyword(s):  
Fundamental Principle ◽  
Atomic Weight ◽  
Considerable Difficulty ◽  
Molecular Weights ◽  
Mass Spectrograph ◽  
Chemical Determination ◽  
Natural Element ◽  
High Degree ◽  
Boyle’S Law

The chemical determination of atomic weights possesses one advantage over physical methods in that it gives the average atomic weight of an element as found naturally, whether that element be a simple one or a mixture of a number of isotopes. Thus, whilst the mass spectrograph method is capable of determining the mass of any isotope to a high degree of accuracy, the evaluation of the abundance ratios of each isotope present in a natural element is often a matter of considerable difficulty. The method which we have used, namely, the microbalance method of limiting pressures, is not new, nor does it involve any new considerations or properties of the gas in question. The fundamental principle involved in the method is a variation of that originally put forward by BERTHELOT in 1898, and known as the method of limiting densities. BERTHELOT showed that gases only obey AVOGADRO’s Hypothesis at zero pressure, and consequently the extrapolation of the ratio of the densities of two gases, measured at a number of pressures down to zero pressure, would lead to the accurate ratio of their molecular weights. Hence, if the molecular weight of one of the gases was known, that of the other could be calculated with ease. In the microbalance method, the pressures of two gases are measured at which they have equal densities as shown by the deflexion of the balance. The ratio of the pressures so obtained would be equal to the inverse ratio of the molecular weights, if both the gases were perfect. In practice, however, owing to the deviations of gases from BOYLE’s LAW, this is only true at zero pressure, and consequently a number of ratios are taken, corresponding to different densities. These, when plotted against the measured pressures of one of the gases, enable the extrapolation to zero to be carried out.

Collaborative Study of the Microanalytical Determination of Phosphorus in Organic Compounds

1973 ◽  
Vol 56 (4) ◽  
pp. 897-900
Author(s):  
Roger A Lalancette ◽  
Al Steyermark ◽  
Ruth Ann Lee ◽  
Donna M Lukaszewski
Keyword(s):  
Phosphoric Acid ◽  
Organic Compounds ◽  
Statistical Evaluation ◽  
Collaborative Study ◽  
Wet Digestion ◽  
Gravimetric Determination ◽  
Two Samples ◽  
Significant Difference

Abstract Sixteen collaborators participated in the study of the determination of phosphorus in organic compounds. Two samples were analyzed by the methods currently in use in the collaborators’ respective laboratories. Samples were combusted by oxygen flask, peroxide fusion, and wet digestion with acid(s). The resulting phosphoric acid was determined either gravimetrically, colorimetrically by the heteropoly blue method, or colorimetrically by the molybdenum yellow method. The various combustion methods were not compared, since there were not enough data to warrant this. The determinative steps were compared, but the data showed no significant difference in either precision or accuracy for any variation. A statistical evaluation of the data showed that the overall mean for the colorimetric heteropoly blue determination of triphenylphosphine (11.81% P) for 4 collaborators is 11.72%; for the colorimetric molybdenum yellow determination for 5 collaborators, 11.70%; and for the gravimetric determination for 3 collaborators, 11.93%. For phenylmethylphosphinic acid (19.97% P), the corresponding values are 19.64, 19.80, and 19.95%.

scholarly journals THE DETERMINATION OF MOLECULAR WEIGHT

1955 ◽  
Vol 33 (5) ◽  
pp. 755-762 ◽  
Author(s):  
A. F. Sirianni ◽  
I. E. Puddington
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
Organic Compounds ◽  
Chemical Stability ◽  
Pressure Difference ◽  
Molecular Weight Range ◽  
Vapor Pressure Difference ◽  
Static Measurement ◽  
Molecular Weights

The molecular weights of organic compounds of known constitution have been determined with satisfactory accuracy, using milligram quantities of materials, by a static measurement of the vapor pressure difference between pure solvents and solutions of the compounds. The method may be used over a considerable temperature range. The suitability of solvents is governed by their chemical stability and vapor pressure. Results obtained using compounds in the molecular weight range of 600–1000 are reported.

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