Semimicro balance

Basically, there is little difference between carrying out experiments on a semimicro (10 to 1,000 mg) scale or on a macro scale. For the smaller quantities, material must be weighed or measured more carefully (using an analytical or semimicro balance and a calibrated pipette), and one uses smaller apparatus. At the lower end of the range, reactions are conveniently carried out in test tubes, which will usually serve as satisfactory aircooled reflux condensers. A simple apparatus which will provide for stirring, the addition of liquid reagents, and drying is shown in Fig. 

One milhliter serum, or a suitable aliquot of lipoprotein solution, was extracted with chloroform-methanol (2 1) by a modification of the procedure of Sperry and Brand (22). The total lipid extract was freed of solvents by evaporation under nitrogen and weighed on a semimicro balance. Infrared analysis of the total lipid by the method of Freeman... 

Semimicro balance reading accuracy 0.01 mg Platinum crucible with lid... 

The n-hexane in the platinum dish or glass dish is vaporized off on the water bath at a maximum of 80 C. Then the dish with the extractable substances is dried at 80 C in the drying cabinet and is then weighed out on a semimicro balance after a definite cooling time in a desiccator. The precautions usual when working in the semimicro range are to be observed. 

The permeabiUty of water vapor was measured by the cup method. The membrane to be measured was fixed on a standard cup half-filled with water. Cups were placed into a chamber with circulating air maintained at constant relative humidity of 37% and at constant temperature of 38"C. The weight of cup with water was quickly measured on an electronic semimicro balance from time to time and the water vapor permeabilily (Pw) was determined by the following relationship ... 

Food Chemicals Codex tests and assays are designed for use with three types of analytical balances, known as micro-, semimicro-, and macro-. 

Electrobalance with a radioactive source in the weighing chamber. Such a balance may be obtained from the Cahn Instrument Company (Gram Electro-balance) and has the advantage over more conventional semimicro- and micro-... 

Depending on the resolution they provide, balances are classed as semimicro- (10 p.g), micro- (1 fxg) or ultramicro- (0.1 p.g) balances. Besides resolution, the (continuously measurable) maximum capacity of the balance is also an important factor. This is particularly the case when measuring inhomogeneous materials where a few milligrams are often hardly representative and a larger sample mass is desirable. 

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