Glass wool, purification

For purification of the product, tubes A and B are cleaned, dried, and reassembled with a dry glass-wool insert in B. Tube C, containing the initially formed product, is attached to tube B as shown in Fig. 2. The system is evacuated and this time left open to the vacuum. The two furnaces are separated by ca. 1.5 cm. Furnace I is heated to 80° and furnace II to 130 to 140°. Sublimation is allowed to continue until all the titanium(IV) iodide has left tube C (12 to 16 hours). The purified product crystallizes in tube B at the separation of the two furnaces. The major impurity, iodine, crystallizes in tube A and in the liquid-nitrogen trap. A fluffy tan residue of negligible weight (0.04 to 0.06 g.) remains in tube C. If desired, further purification can be accomplished by moving tube B farther into furnace II, which results in a second sublimation of the product. 

Traces of water or acidic impurities can lead to the formation of insoluble, hydrated lanthanide adducts, or of paramagnetic lanthanum oxide80, adversely affecting spectral resolution. Careful purification of the solvents and substrate is advised, and filtration of the solution through glass-wool or cotton plugs may be useful. 

Preparation of Niobium (Tantalum) Chloride and Purification from Iron Impurities. Assemble an apparatus as shown in Fig. 124. Place activated carbon preliminarily dried in vacuum during two hours at 200-250 Cinto section III of the reactor. Mix 2 g of niobium (tantalum) and 0.5 g of iron in a porcelain boat and place them in section I. Fill columns 5 and 6 with a mixture of glass wool and phosphoric anhydride, and fill wash bottle 7 with sulphuric acid. 

Any ice present in the product can be removed by filtration of the cyclopentadiene through glass wool. Cyclopentadiene can be stored at Dry Ice temperatures in a tightly capped bottle for several weeks without serious loss due to dimerization. Purification of a stored sample can be effected by distillation through a short Vigreux column at 10-30 nun. pressure and collection of the product in a receiver cooled by a Dry Ice-acetone bath until... 

A mixture of 175 g. (1.11 moles) of methyl a,/3-dichloropropionate (p. 202) and 500 ml. of 20% aqueous hydrochloric acid is refluxed for 5 hours, after which it is cooled and filtered through glass wool. The filtrate is extracted with three 100-ml. portions of chloroform. After the extract has been dried over sodium sulfate, the chloroform and low-boiling components are removed by distillation under reduced pressure. The yield of crude product in the residue from the distillation is 105 g. (65%). Further purification by distillation gives a product boiling at 130-133V26 mm. and melting at 49-50°. 

---