Bubbles, glass-blowing

Only freshly cut surfaces, not touched by fingers, should be sealed. When it is Impossible to trim an end piece in order to obtain a freshly cut surface, heat the area with a torch and pull off some glass with the aid of a glass rod, or melt the glass, blow this area into a thin-wall bubble and strip it off. 

This tube is drawn out in the flame of a blow-pipe from glass tubing 4-8 mm. wide and is then drawn out again to sufficient fineness in a micro-flame. To make sure before use that the capillary is not closed, the tip is submerged in ether in a small test tube and air is blown in from the mouth. The bubbles should emerge separately and slowly. Capillaries for distillation in a high vacuum should emit air bubbles only on powerful blowing, and then with difficulty. 

Stability of both foam and asymmetric aqueous films at the surface of organic liquids of different polarity has been studied as function of the surfactant concentration [551], Microscopic foam films were obtained in a glass cuvette (Tig. 3.120,c) by blowing an air bubble at the tip of a vertical capillary immersed into the surfactant solution. With a micrometric screw (not shown in the figure) the bubble was pressed carefully onto the solution/air interface, thus forming the film. 

The blowpipe is now passed to another member of the team. He shapes the gob by skilful manipulation and then blows an air bubble into the molten glass. 

How do we know that it was COj that caused the change Take a clean glass and prepare another solution with four teaspoons water (20 milliliters) and two drops of fish-tank indictor. Now blow up a balloon. Holding the balloon pinched shut, put the balloon on one end of a straw and put the other end of the straw down into the indicator solution. When you ease open the neck of the balloon, freshly exhaled COj from your lungs will bubble quickly through the solution and you should see the indicator once more turn from green-blue to yellow. 

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