Some density determinations

It was required to determine the densities of small quantities of metallic elements to an accuracy of about one part in 10,000, and this paper is an account of some of the work undertaken to reach that end. In the course of the work, the densities of the following substances have been determined :─ (1) Carbon tetrachloride. (2) Ethylene dibromide. (3) Cadmium. (4) Lead and isotopic lead from uranium ore. Kahlbaum who has made the most exhaustive study of the density of metals, states that the determination of specific gravity of metals is a delicate matter which can only be effected with success on large quantities of substance, and one cannot attribute to the result the general character of a physical constant for the metal; the determined value belongs exclusively to the sample on which the determination is carried out. These statements are in our opinion too sweeping ; but in this paper it is only intended to describe an improvement in density measurements which renders possible determinations with accuracy on comparatively small samples, and to give a few illustration of the effectiveness of the method.

Download Full-text

A SIMPLE RAPID METHOD FOR DETERMINATION OF SPECIFIC GRAVITY OF SMALL SAMPLES OF URINE

PEDIATRICS ◽

10.1542/peds.24.5.814 ◽

1959 ◽

Vol 24 (5) ◽

pp. 814-818

Author(s):

Allen S. Goldman

Keyword(s):

Specific Gravity ◽

Present Report ◽

Total Sample ◽

Mineral Oil ◽

Small Samples ◽

Gradient System ◽

Small Opening ◽

Flotation Method ◽

Made In

THE THERAPY of infants with disturbances in fluid balance is greatly assisted by knowledge of the specific gravity of the urine. Frequently only a few milliliters can be collected at any one time, while a minimum sample of 25 ml is necessary for use of the smallest urinometers currently available. The existing methods of determining specific gravity of one drop of urine are somewhat laborious, and require expensive equipment and the services of a relatively skilled technician. The present report describes a method which is rapid and simple and requires only a few drops of urine in its use. It is similar in principle to the determination of specific gravity of blood by the copper-sulfate method. For use with urine, mixtures are employed of two relatively nonvolatile liquids, immiscible with water, and with specific gravities nearly equally above and below the range in urine. The specific gravity of urine is determined by allowing one drop to fall into each of a series of tubes containing a mixture of the two liqquids made up to various specific gravities ranging from 1.005 to 1.030 (Fig. 1). That mixture in which the drop of urine comes most nearly to remaining still (neither rising nor falling after coming to rest) approximates the specific gravity of the urine. The total sample needed is only a few drops, which can be quite small if a dropper with a small opening (2 mm) is used. The determination takes a few minutes. A year's supply of the mixtures can be made in one afternoon and costs less than $6.00. MATERIALS The two solutions used were selected from the flotation method of Kirk, using a density gradient system. These are Liquid 1, dibutyl-n-phthalate (Eastman), specific gravity 1.04820°; and Liquid 2, kerosene, specific gravity 0.8220°. (Similar results were obtained by substituting California mineral oil, specific gravity 0.842-0.88420°, for kerosene.)

Download Full-text

Improved Codistillation Method for Determination of Carbon Tetrachloride, Ethylene Dichloride, and Ethylene Dibromide in Grain and Grain-Based Products

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/68.4.759 ◽

1985 ◽

Vol 68 (4) ◽

pp. 759-762

Author(s):

Jonathan W Devries ◽

Paul A Larson ◽

Raymond H Bowers ◽

Joyce A Keating ◽

James M Broge ◽

...

Keyword(s):

Carbon Tetrachloride ◽

Internal Standard ◽

Ethylene Dichloride ◽

Standard Mixture ◽

Ethylene Dibromide ◽

Acetone Water ◽

Relative Standard ◽

The Common ◽

Hexane Solution

Abstract A method is described for the determination of the common fumigants carbon tetrachloride (CC14), ethylene dichloride (EDC), and ethylene dibromide (EDB) in grain and grain-based products. A properly prepared sample is mixed with water and hexane, an internal standard mixture of 1,2-dichloropropane (DCP) and 1,2-dibromopropane (DBP) is added, and the fumigants are codistilled with the hexane into an appropriate receiver. After the hexane solution is dried over sodium sulfate, the quantities of fumigants present are quantitated on a gas chromatograph (GC) equipped with an electron capture detector (ECD). For the matrices investigated, the relative standard deviation of the method was 6.0,9.7, and 23.1% for CC14, EDC, and EDB, respectively. Recoveries of added fumigants were 107, 95, and 101%, respectively. Comparison with an acetone-water soak extraction method gave a correlation of 0.967 between methods for EDB with odds of a difference between methods of 35%.

Download Full-text

Modification of the AOAC Method for Determination of Fumigants in Wheat

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/63.3.539 ◽

1980 ◽

Vol 63 (3) ◽

pp. 539-545

Author(s):

Marion Clower Jr

Keyword(s):

Carbon Tetrachloride ◽

Constant Current ◽

Ethylene Dichloride ◽

Surveillance Program ◽

High Recovery ◽

Ethylene Dibromide ◽

Aoac Method ◽

Liquid Chromatographic ◽

Lower Limits

Abstract The official first action AOAC method for determination of residues of fumigants in grains has been modified for use by 6 laboratories in an FDA pesticide surveillance program. A 15% OV-I7 gas-liquid chromatographic column, installed in a chromatograph equipped with a constant current 63Ni electron capture detector, provides for improved resolution, multiresidue capability, and lower limits of detection. A study was made of the behavior of chloroform, carbon tetrachloride, ethylene dichloride, trichloroethylene, tetrachloroethylene, and ethylene dibromide through the method. Recoveries from fortified wheat samples averaged 105-115%. Experimental evidence is presented which suggests that part of the consistent trend toward high recovery can be attributed to selective sorption of acetone by the CaCI2 used in the final drying step.

Download Full-text

III. Methods. C. Total Volatile Organic Halide Determination of Aggregate Residue of Carbon Tetrachloride, Ethylene Dichloride, and Ethylene Dibromide in Fumigated Cereal Products: Determination of Bromide by the Kolthoff-Yutzy-Van Der Meulen Procedure and of Ethylene Dichloride by Difference

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/40.1.180 ◽

1957 ◽

Vol 40 (1) ◽

pp. 180-185

Author(s):

D A Mapes ◽

S A Shrader

Keyword(s):

Carbon Tetrachloride ◽

Ethylene Dichloride ◽

Total Volatile ◽

Ethylene Dibromide ◽

Organic Halide ◽

Cereal Products ◽

Volatile Organic

Download Full-text

Method for Determining Multiple Residues of Organic Fumigants in Cereal Grains

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/53.4.742 ◽

1970 ◽

Vol 53 (4) ◽

pp. 742-746

Author(s):

Bernadette Malone

Keyword(s):

Carbon Tetrachloride ◽

Acid Medium ◽

Electron Capture ◽

Carbon Disulfide ◽

Methyl Bromide ◽

Cereal Grains ◽

Ethylene Dichloride ◽

Ethylene Dibromide ◽

Solvent Residues

Abstract A method is described for determination of residues of the fumigants methyl bromide, carbon disulfide, chloroform, ethylene dichloride, carbon tetrachloride, and ethylene dibromide in cereal grains. Whole or ground grain is boiled in an acid medium, and the volatile fumigants are dried and collected in cold solvent. Residues are determined by analyzing aliquots of the collected solution by electron capture GLC. Recoveries range from 59 to 105%. Extraction appears to be complete in the 2 hr boiling period specified. An unexplained conversion of carbon tetrachloride to chloroform is described.

Download Full-text