scholarly journals A method of determination of some biologically important aldehydes and ketones, with special reference to pyruvic acid and methylglyoxal

1932 ◽  
Vol 26 (6) ◽  
pp. 1788-1799 ◽  
Author(s):  
Francis Paul Clift ◽  
Robert Percival Cook
Keyword(s):  
Special Reference ◽  
Pyruvic Acid ◽  
Method Of Determination ◽  
Aldehydes And Ketones

Determination of the Water Absorption of Crude Rubber and of Vulcanized Rubber

1940 ◽  
Vol 13 (2) ◽  
pp. 400-407
Author(s):  
J. W. van Dalfsen
Keyword(s):  
Special Reference ◽  
Water Absorption ◽  
Vulcanized Rubber ◽  
Method Of Determination ◽  
Determination Methods

Abstract In the introduction the purpose of the investigation is described which is the development of a method suitable for the determination of the water absorption of crude and vulcanized rubber, and which, in conjunction with ash and nitrogen determinations is especially adapted to the testing of purified rubber. The conditions which affect the results of water determinations are reviewed, with special reference to the formulas of Taylor and Kemp, which make it possible, within certain limits, to compare results obtained by different determination methods. The reasons for selecting the foregoing method of determination of water absorption are described. It is pointed out that water absorption depends to different degrees on the time of vulcanization. In the rubber-sulfur mixture which was chosen, the influence of the degree of vulcanization is small, so that it is sufficient to vulcanize all types of rubber for the same length of time. At the same time it is shown that the results obtained by immersion of rubber for 7 and 25 hours at 80° C. still sufficiently agree with the values computed from the formulas of Taylor and Kemp. A method of measuring water absorption is described in detail. The question arises to what extent rubber manufacturers may use this method, in conjunction with ash and nitrogen determinations, method for estimating the quality of purified rubber. Rubber manufacturers are urged to give their opinion of this proposed method. Some other method will be considered if it should appear that manufacturers prefer this other method.

Development of a method for multielemental determination in water by EDXRF with radioisotopic source of 238Pu.

2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Camilo Fuentes Serrano ◽  
Juan Reinaldo Estevez Alvares ◽  
Alfredo Montero Alvarez ◽  
Ivan Pupo Gonzales ◽  
Zahily Herrero Fernandez ◽  
...  
Keyword(s):  
Thin Layer ◽  
Expanded Uncertainty ◽  
Considerable Decrease ◽  
X Ray ◽  
Precipitation Efficiency ◽  
Method Of Determination ◽  
Sensitivity Curves ◽  
Order Of Magnitude ◽  
Metrological Parameters

A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of 238Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively. The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of 238Pu instead of 109Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative. Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).

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