Apparatus with standard ground joints

The highest degree of purity is attained by using apparatus with standard ground joints (see e.g. Fig. 47) its sole disadvantage is its rather high price. 

Engler dietillation apparatus with standard ground joint... 

For controlling the temperature of baths or flowing liquids and of various portions of an apparatus (such as column jackets, tube heaters, etc.) contact thermometers are largely used they are obtainable with standard ground joints (e.g., NS 14.5). Contact thermometers can be obtained either with contacts set to definite temperatures or with variable temperature. In the variable type (Fig. 366) the upper thermometer scale is used to set the required temperature, while the lower one carries the electrical contact. A contact thermometer with a spiral bulb with a large surface area (Fig. 367a)... 

For recrystallization of air-sensitive prQjarations and, in general, for production of pure preparations, an apparatus devised by Ulich (Fig. 49) is used more advantageously [H. Ulich, Chem. Fabrik 278 (1931) a similar apparatus but with standard ground joints is given by F. 

The Kjeldahl flasks used should be made of borosilicate glass or silica (100- to 250-ml nominal capacity) fitted with an extension to the neck by means of a standard ground joint. The extension serves to condense fumes into an acid-fume condenser and carries a tap funnel through which the reagents are introduced. A suitable apparatus is shown in Fig. 22. 

Rapidly connect the receiver with the silicochloroform via standard ground-glass joint 3 to an apparatus for fractional distillation under atmospheric pressure (see Fig. 20) and close side arm 4 (see Fig. Ill) with a glass stopper. Perform distillation and gather the fraction boiling at 34-37 °C. 

The apparatus consists of a glass reaction flask fitted with a side arm and dropping funnel. The side arm is connected to two glass traps in series by means of standard ground-glass joints and stopcocks. 

Apparatus fitted with standard-taper ground-glass joints is convenient for this preparation. 

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