NEW CRYOPHORUS FORMS ROSS A. BAKER College of The City of New York, New York
A SMALL GIRL
once explained that when she wanted fill it with bromine gas at ordinary temperatures. to draw a picture, all she had to do was to get an idea When the test tube end is immersed in a dry ice sludge, a button of solid crystalline bromine quickly collects, and put a lime around it. This youngster is a challenge to a chemistry teacher: leaving the flask quite colorless. When dislodged, the when he gets an idea, he should he able to put glass solid button makes an interesting plaything as it dances around it. This is particularly true of the lecture around the walls of the flask like a Mexican jumping demonstrator who is constantly evolving new setups bean. Several years ago a cryophorus' was devised to meet to meet changing conditions. A rudimentary howledge of glassblowing is a must in the training of every ' a specific need. It proved so successful in lecture chemistry teacher. Unless he can test his ideas while demonstration that a considerable number were conthey are fresh, they are prone to atrophy. There is structed for individual student use. Ingenuous student nothing quite so deadening as to he limited to ready- questions have prompted a number of modifications, one of which seems worthy of demonstration here. It made equipment. The actual requirements are surprisingly simple, and is designed to prove that a liquid is cooled by its own consist for the most part of adaptations of flasks and evaporation even though the molecules which have bulbs which serve as housings. Of course one must just left it may be heated a moment later. This is accomplished by inserting a "hot finger" in the path make the necessary seals and bends. A very simple device for illustrating the effect of of the escaping water molecules. In this hot finger, temperature on vapor pressure may be made from a alcohol may be burned continuously. The heated 1-5-liter round-bottom flask. An 8-mm. tube is first water vapor then travels to the "cold finger" where a sealed to the bottom. This is used as a handle while sludge of dry ice freezes it and thus maintains the most of the old neck is removed. The short stump "one way traffic." is rounded to a test tube end. Then the flask is B m m , R. A,. "The American Physics Teacher," 1939,Val. evacuated and enough liquid bromine introduced to VII, p. 424. 259
