Wool glass

The apparatus shown in Fig. 38 can also be used for fractionation by placing a secure plug of glass wool at the base of the vertical condenser and then filling it with short pieces of glass tubing. 

Lead formate separates from aqueous solution without water of crystallisation. It can therefore be used for the preparation of anhydrous formic acid. For this purpose, the powdered lead formate is placed in the inner tube of an ordinary jacketed cond ser, and there held loosely in position by plugs of glass-wool. The condenser is then clamped in an oblique position and the lower end fitted into a receiver closed with a calcium chloride tube. A current of dry hydrogen sulphide is passed down the inner tube of the condenser, whilst steam is passed through the jacket. The formic acid which is liberated... 

Potassium Hydroxide, Alcoholic. Boil under reflux a mixture of 10 g. of powdered KOH and 100 ml. of rectified spirit for 30 minutes. Cool and if solid material remains, decant through a filter of glass-wool. 

Fig. 77,13, 1 illustrates a distillation unit when it is desired to protect the distillate from moisture in the atmosphere. The drying tube may be filled with anhydrous calcium chloride held in position by loose plugs of glass wool or with a loose plug of cotton wool. Fig. 77,13, 2 depicts the use of an air condenser for liquids of boiling point above 140-150°. 

Filtration of corrosive liquids with suction. A strongly alkaline or acid suspension is best filtered through a sintered glass funnel. Alternatively, glass wool or asbestos may be plugged into the stem of a glass funnel or supported upon a Witt plate in a glass funnel. 

The solid in the tower may be supported on a Witt filter plate, but a plug of glass wool is satisfactory the plug of glass wool above the solid acts as a filter for fine particles of the desiccant. 

Solid magnesium must be absent to avoid the formation of diallyl via allyl magnesium bromide the insertion of a short plug of glass wool effectively removes any finely divided magnesium. 

Pack the catalyst into a Pyrex combustion tube about 90 cm. long and 15 mm. bore, and place plugs of glass wool at 25 cm. intervals inseit into a tube furnace and adjust to a temperature of 330° full details of the complete apparatus are given in Section 111,72 and Fig. Ill, 72, 1. 

If the outlet of the siphon tube at the bottom of the Soxhlet apparatus is well plugged with cotton wool so that no finely-divided bariuna hydroxide can pass into the flask, the barium hydroxide may be placed directly into the extractor until the latter is three-quarters full the remaining space is filled with glass wool. 

Chlorine from a cylinder is passed through two wash bottles containing concentrated sulphuric acid, then through an empty wash bottle filled with glass wool to remove spray. 

It is advisable to filter the a-picolyl-lithium solution rapidly through a thin layer of glass wool (to remove any unreacted lithium) on to the solid carbon dioxide. 

If a clear solution of n-butyl-lithium is required for any purpose, it may be decanted through a glass wool plug as detailed under 2-Phenylpyridine, Note 4. 

---