Glass hygroscopicity

The absolute ethanol obtained in this way should have d., o 794, It is very hygroscopic, and the bottle in which it is stored should preferably have a well fitting ground-glass stopper alternatively, the bottle can be closed with a tightly fitting rubber stopper but not with a cork, as corks contain appreciable quantities of water. 

Evaporate the beaker contents to dryness on a glass plate In the oven to collect the crystals of Methylamine HCI (hygroscopic ). The yield should be approximately 15g (95%). 

Tellurium Tetrafluoride. TeUurium tetrafluoride [15192-26-4] TeF, forms white, hygroscopic needles melting at 129.6°C. It decomposes at 194°C to TeFg and is readily hydrolyzed. Tellurium tetrafluoride attacks glass, sUica, and copper at 200°C, but it does not attack platinum below 300°C. 

Titanium tetrabromide [7789-68-6] M 367.5, m 28.3°, b 233.5 , d 3.3. Purified by distn. Distillate forms light orange hygroscopic crystals. Store in the dark under N2 preferably in sealed brown glass ampules. [Olsen and Ryan J Am Chem Soc 54 2215 1932.]... 

In all cases the crucible is allowed to cool in a desiccator, and, before it is quite cold, the solid is transferred to a warm, dry glass-stoppered tube or bottle, out of which, when cold, it may be weighed rapidly as required. It is important to remember that anhydrous sodium carbonate is hygroscopic and has a tendency to change into the monohydrate. 

Procedure Weigh 200 g sodium dichromate and transfer to a 2 Litre hard-boroslicate glass beaker. Dissolve it in 100 ml of water and cool in an ice-bath to about 10-15°C. Now, add to it 1500 ml of sulphuric acid (3 6 N) in small bits at intervals with constant stirring. Chromic acid mixture is extremely corrosive and hygroscopic and must be stored in closed glass-stoppered bottles. 

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