Alkali fusion apparatus

The fusion apparatus described on page 87 (Fig. 14) is placed directly over a small Fletcher burner and charged with 200 grams of solid, chlorate-free sodium hydroxide in large sticks, and 60 cc. water. (Fusions using chlorate-containing alkali give lower yields and are. 

Defoamers are used in fibre finishes in order to inhibit the formation of foam during the manufacturing and application of the finishes. Silicones and fluorochemicals are outstanding defoamers. They have very low surface tension and limited solubility in many organic compounds. They can quickly reduce the local surface tension of bubbles to create an imbalance of surface tension which leads to the easy rupture of bubbles. Silicones can be analysed using FUR. The analysis of fluorochemicals is difficult because fluorochemicals, especially perfluoro compounds, are resistant to many reagents. One microdetermination of fluorine by alkali fusion in a metal bomb was reported. Since it is too complicated and specialised apparatuses are used, this method is not introduced here. 

Silver apparatus. The chief uses of silver crucibles and dishes in the laboratory are in the evaporation of alkaline solutions and for fusions with caustic alkalis in the latter case, the silver is slightly attacked. Gold vessels (m.p. 1050 °C) are more resistant than silver to fused alkalis. Silver melts at 960 °C, and care should therefore be taken when it is heated over a bare flame. 

Nickel ware. Crucibles and dishes of nickel are employed for fusions with alkalis and with sodium peroxide (CARE ). In the peroxide fusion a little nickel is introduced, but this is usually not objectionable. No metal entirely withstands the action of fused sodium peroxide. Nickel oxidises in air, hence nickel apparatus cannot be used for operations involving weighing. 

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