Magnesium stocks

Magnesium stock solution, 1000 pg Mg + mb - dissolve 1.6581 g magnesium oxide (previously dried at 105°C overnight and cooled in a desiccator) in the minimum of hydrochloric acid (approximately 5 M). Dilute with water to 1 I in a volumetric flask to obtain a solution of 1000 pg Mg2+ mM. 

Magnesium stock solution—using distilled or deionized water prepare six magnesium standards in 100 ml volumetric flasks of 0.1, 0.3, 0.4, 0.5, 0.6, and 0.8 pg mk concentration from the stock solution. Also prepare 250 ml of a 0.2 pg mpi magnesium standard. 

All solutions are made with deionized distilled water and are prepared from AnalaR chemicals (British Drug Houses, Poole, England) with the exception of the magnesium and calcium stock solutions. The calcium solutions are made from Specpure calcium carbonate (Johnson, Matthey Co. Ltd., London) dissolved in the minimum volume of concentrated HCl. The magnesium stock solution is prepared from Specpure magnesium sulfate. Polythene containers are used to store all solutions. 

Magnesium Stock Solution I. A solution of 25 mM MgS04-7H20, the concentration of which is checked by titration with disodium ethylene-... 

Assay of luciferin. A buffer solution of 20-50 mM Tris-HCl (pH 7.2 1.9 ml) containing 20 mM magnesium acetate and luciferase (typically 0.1 ml of the luciferase stock solution) is injected into a vial containing luciferin sample (1-10 pi) and 20 mM KCN (0.1 ml made daily in 0.1 M Tris-HCl buffer, pH 7.2), and the resulting light emission is measured in terms of total light. 

Stock solutions of 2-propenylmagnesium bromide (1-2 M) in diethyl ether and 2-propenyl-magnesium chloride in THF are commercially available. 

A detailed study of the phase relationships in the magnesium oxysulphate cement was carried out by Urwongse Sorrell (1980b). They used X-ray analysis to examine the phases present in the cement, and established the composition of the invariant liquids after equilibration by measuring specific gravity with the aid of a pycnometer. Specific gravities were related to concentration by means of a calibration exercise in which 30 stock solutions of sulphuric acid at concentrations between 0 and 79-5 wt % were prepared with distilled water. 

There are many compounds that contain boron and hydrogen, and they are known collectively as the boron hydrides. Six boron hydrides were prepared by Alfred Stock in 1910-1930 by the addition of hydrochloric acid to magnesium boride that was produced in small amounts when B203 was reduced with magnesium. 

As was discussed in Chapter 13, hydrogen does not react directly with some elements, so the hydrides must be prepared in a different way. Alfred Stock prepared silicon hydrides by first making the magnesium compound, then reacting it with water. 

Metabolic Balance Methods. Theoretically, the amount of mineral retained in the body should be determinable by balance methods. Heroux and Peter (50) attempted to do this for calcium and magnesium in rats fed three diets. For rats fed their stock diet, they predicted from balance data that the carcasses would contain 23.8 g calcium and 605 mg magnesium. By analysis, the carcasses contained 4.45 g calcium and 152 mg magnesium. However, the relationship between calcium balance data (X) and carcass data (Y) were closely related (Y = 1.05X -. 03, r = 0.99 for group mean data) in the rat data of Whittemore et al. (51). 

Design an investigation to determine the value of n in the rate law equation. Assume that you have a stock solution of 6.0 mol/L HCl, magnesium ribbon, a stopwatch, and any standard laboratory glassware available. If you want to carry out your investigation, have your teacher approve the procedure first. 

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