Hemi-Macro Method

Whilst the ultimate ideal in organic analysis is the general adoption of micro methods, it has to be appreciated that such ideals cannot always 

A simple method for the determination of C and H is that of Roger and McKay (loc. cit.). Amounts of substance from 20—40 mgs. are used and the heating mortar of the Pregl method is dispensed with and simple fillings of the macro type are used in the combustion tube. 

In filling the tubes a small wad of glass wool is first placed over the perforated glass plate. In the case of the soda lime tube, a layer (1—1-5 cms.) of Ca 2 is then placed on this wad and is held in place by another small wad of glass wool. The rest of the tube is filled with soda lime capped with a small glass wool wad. The stoppers must be carefully 

The CaCla tube is attached with a piece of pressure tubing to the snout end of the combustion tube through the tube entering the glass bell. The first soda lime tube is attached to the CaC tube through the small tube entering under the stopper. The second soda lime tube is attached to the exit tube of the first in a similar manner. The absorption train is protected with a small tube containing CaClj and soda lime. 

The first stage in the weighing operations is the wiping of the absorp- 

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The Carius method can be worked on a micro (see Pregl, loc. tit.) or hemi-macro scale. Halogens can be estimated by other methods (see, inter alia, Bobranski and Sucharda, loc. tit.) in which the substance is completely oxidised in the dry state, Cl and Br being trapped in solid BaC03,1 in Na2S03 in a special apparatus. 

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