Capping stabilisation

An old bottle (1 year) containing glycolonitrile with phosphoric acid used as a stabiliser showed the appearance of tars. It detonated during handling. The detonation was probably due to the polymerisation of nitrile that was made possible by the fact that phosphoric acid was isolated by tars. Besides, the cap was cemented by tars that had already formed round the cap. A similar accident happened thirteen days after distilling the same nitrile. 

Notes. (1) Acrolein is usually supplied in sealed amber-coloured ampoules stabilised by the addition of a little hydroquinone. The ampoule should be cooled thoroughly before being opened with great care. It has been recorded that opened samples of acrolein stored in screw-capped bottles may explode violently, presumably as the result of rapid exothermic polymerisation. 

Since the parent //-capped compound was thought capable of detonation, this protected and supposedly stabilised derivative was isolated. A slow decomposition with light emission was remarked while handling it, caution and screens are recommended in handling it. 

Most CoraUium coral is bleached before being worked, to clean off any impurities. This is also supposed to bring out the colour of the material. However, if it is overdone, the surface can be damaged, and the high lustre will in time deteriorate to a dull, opaque finish. Blue coral and red soft coral can be capped with plastic to stabilise them. They can also be backed with plastic to give more bulk (Fig. 11.7). 

Some gem quality pieces of ammolite are stabilised with epoxy or other resin before cutting, to prevent the delicate surface from flaking. However, some material is cut without prior treatment. The cut pieces are then polished, and finished in one of three ways. The most valuable and rare pieces are solid shell, with no matrix on the back. Thinner slices are made into doublets to reinforce the material by adding an extra layer of natural matrix on the back. Triplet stones have both an extra matrix back, and a cap of synthetic spinel or quartz. 

Somewhat higher reduction guidelines resulted from the stabilisation approach. Here, the cap for the emissions trading segment would have had to amount to 12 or 16 Mt CO2. 

---