Chemistry and Physics. 407 



is placed in a large beaker and surrounded with a freezing mix- 

 ture of ice and salt. Within this test tube is the bulb of an air 

 thermometer cylindrical in form, 12 cm. long and 1*5 cm. in diam- 

 eter, the tube of which, about 10 cm. long and 1*5 mm. in bore, 

 is bent twice at right angles, its end dipping in a vessel of colored 

 water. Upon the larger upright portion of this tube two bulbs 

 are blown to act as safety bulbs ; one near the top to prevent the 

 liquid from passing over into the thermometer-cylinder on con- 

 traction and the other near the bottom to prevent the escape of 

 .any air from the thermometer when it is heated. The freezing 

 point of water is first obtained with the apparatus. For this pur- 

 pose the test tube is filled with distilled water, the thermometer 

 bulb inserted into it, the whole placed in the freezing mixture and 

 the water constantly agitated by means of a stirrer. The column 

 of colored water rises in the tube as the cooling goes on, reaching 

 at first a higher than the normal point, owing to surfusion, but 

 suddenly falling to this as soon as the formation of ice begins, 

 remaining then stationary. The motion of the column can be 

 readily seen throughout an ordinary lecture room, the position of 

 rise being indicated on an attached scale or marked with a slip of 

 paper. If now the experiment be repeated with various solutions 

 each containing in the same quantity of water (say 100 c. c.) 

 molecular quantities of different organic substances, it will be 

 observed that the height of the colored column, while approxi- 

 mately the same in each case, is always greater than when pure 

 water is used. With solutions of 34*2 grams cane sugar, 18*2 

 grams mannite, 5 - 8 grams acetone, 6"0 grams glacial acetic acid, 

 in 100 c. c. water for example, the difference in height is several 

 centimeters and is therefore visible from a considerable distance. 

 The solutions may be prepared during the lectures and in this 

 way it can be clearly demonstrated that isotonic solutions cause 

 the same depression of the freezing point. The difference is 

 greater if an electrolyte be used. In a solution of 5 "85 grams 

 sodium chloride in 100 c. c. water, this difference is nearly twice 

 that obtained with the organic solutions. — Ber. Berl. Chem. 

 Ges., xxii, 31, January, 1889. G. f. b. 



3. On Ghydraza'ine or Protoxide of Ammonia. — Matjmem; 

 has described a gas obtained by the action of permanganic acid 

 upon ammonium oxalate, to which he has given the formula 

 N 2 H 6 and the name chyclrazaine. To prepare it, 158 grams of 

 potassium permanganate, 141*2 grams crystallized ammonium 

 oxalate and sulphuric acid equivalent to 40 grams 30 3 , are mixed 

 in a flask holding 6 liters and heated to 100° on a water bath. A 

 second inverted flask placed above the first acts as a condenser; 

 and a tube from this conducts the evolved gas into an acid whei'e 

 it is condensed, nitrogen only escaping. In the inverted flask 

 beautiful crystals of chydraza'ine bicarbonate are deposited. If 

 hydrogen chloride be used to absorb the gas, the liquid yields 

 on evaporation the hydrochlorate in minute crystals, very soluble 

 in water, scarcely soluble in alcohol. The sublimed hydrochlorate 



