Semimicro operations

Schwinger filter, 1107 still head, 1103, 1105 with interchangeable ground glass joints, 1109, 1110 Semimicro operations ... 

XII,2. SOME TYPICAL OPERATIONS ON THE SEMIMICRO SCALE 1. Distillation at atmospheric pressure.—A simple apparatus is shown in Fig. XII, 2, 1 the pear-shaped distilling flask with long side... 

The scale of the recrystallisation envisaged in group (1) means that the operations are carried out in the conventional manner but in apparatus of reduced size. Thus small conical flasks (5 to 20 ml), pear-shaped flasks (5 to 20 ml), semimicro test tubes (75 x 10mm or 100 x 12mm) or centrifuge tubes (1 to 5ml)... 

II.4 SEMIMICRO APPARATUS AND SEMIMICRO ANALYTICAL OPERATIONS The essential technique of semimicro analysis does not differ very greatly from that of macro analysis. Since volumes of the order of 1 ml are dealt with, the scale of the apparatus is reduced it may be said at once that as soon as the simple technique has been acquired and mastered, the student will find it just as easy to manipulate these small volumes and quantities as to work with larger volumes and quantities in ordinary test-tubes (150 x20 mm) and related apparatus. The various operations occupy less time and the consumption of chemicals and glassware is reduced considerably these two factors are of great importance when time and money are limited. Particular care must be directed to having both the apparatus and the working bench scrupulously clean. 

Wash bottles For most work in semimicro analysis a 30 or 60 ml glass stoppered bottle is a suitable container for distilled water the latter is handled with a reagent dropper. Alternatively, a bottle carrying its own dropper (Fig. II. 14a or b) may be used. A small conical flask (25 or 50 ml) may be used for hot water. For those who prefer wash bottles, various types are available (Fig. 11.19) a is a 100 or 250 ml flat-bottomed flask with a jet of 0-5-1 mm diameter, and is mouth-operated b is a hand-operated wash bottle (flask, 125 ml rubber bulb, 50 ml) c is a Pyrex 50 ml graduated wash bottle, and d is a polythene bottle, from which the wash solution can be obtained by squeezing. 

Transferring of precipitates In some cases precipitates can be transferred from semimicro test-tubes with a small spatula (two convenient types in nickel or monel metal are shown in Fig. 11.20). This operation is usually difficult,... 

In micro analysis the scale of operations is reduced by a factor of 0-01 as compared with macro analysis. Thus whereas in macro analysis the weights and volumes for analysis are 0-5—1 g and about 10 ml, and in semimicro analysis 50 mg and 1 ml respectively, in micro analysis the corresponding quantities are about 5 mg and 0-1 ml. Micro analysis is sometimes termed milligram analysis to indicate the order of weight of the sample employed. It must be pointed out that whilst the weight of the sample for analysis has been reduced, the ratio of weight to volume has been retained and in consequence the concentration of the individual ions, and other species, is maintained. A special... 

Solutions are separated from precipitates by centrifuging. Semimicro centrifuges (Section II.4.5), either hand-operated or electrically-driven, can be used. Adapters are provided inside the buckets (baskets) in order to accommodate micro centrifuge tubes with narrow pen ends. 

For the cations, a limited number of preliminary reactions should be studied first, followed by an analysis of a mixture or solution containing a member or members of each group. This will give practical experience in the routine operations of semimicro analysis and also provide practice from the very outset in the use of Group Separation Tables. Particular attention should be paid to ... 

The book begins with a discussion of the basic physico-chemical aspects of reactions utilised in qualitative inorganic analysis. A description of laboratory equipment follows, and operations which include semimicro and micro techniques, and simple electrochemical, spectroscopic and chromatographic methods. The reactions of the most important cations and anions are described, followed by a treatment of systematic qualitative analysis. Sample preparation, dissolution and fusion of insoluble materials are treated in detail. A separate chapter deals with the reactions of less common ions, with guidelines to their separation and identification in the course of systematic analysis. Finally, a simplified course of qualitative analysis is given this chapter will be particularly useful where the time allocated to qualitative analysis is limited. 

Fig. 43. Operation of semimicro separatory tube with one hand...

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