STEAM AND BRINES. 533 



from a plumber, by getting him to fit a neck to one of the copper balls which are used 

 as controlling floats for cistern taps. These are to be had of all sizes up to 1 inches 

 diameter, and are very cheap. 



The receiver, C, has the appearance and shape shown in the fig. The actual dimen- 

 sions are variable, according to the quantity of salt on which it is proposed to operate, 

 and according to the length of the thermometer. The working part of the thermometer 

 must be entirely within the receiver. The uncertainty caused by the exposure of any 

 part of the stem occupied by mercury stultifies the use of very delicate instruments. 

 If the whole range of the thermometer is to be utilised, then the length of the receiver 

 must be such as to take the whole thermometer. The two thermometers which I used 

 in all my experiments differed slightly in length, and it was convenient to have a 

 receiver made for each. Of course the longer thermometer could be used with the 

 shorter receiver, so long as the temperature to be observed was not too high. One 

 receiver which I have used much has the following dimensions : — Total length of the 

 body of the tube, from the entrance, a, of the steam tube at the bottom to the top, c, 

 where the thermometer, F, is retained by a perforated cork, is 30 cm. ; the length, a b, of 

 the body for the reception of the salts and brine is 16 cm., and its diameter 42 mm. 

 The length of the neck, be, is 14 cm. and diameter 13 mm. The steam exit tube, d, 

 has a diameter of 7 mm., and the entry or connecting tube, e, has the same or a slightly 

 less diameter. The entry tube is bent up parallel to the main body of the instrument, 

 and is connected with the boiler by a tube, G, as shown in the fig. The steam tube, C, 

 on the boiler is important. The straight portion which enters the boiler should have a 

 diameter of 8 to 9 mm. Its upper part, which is fitted with a cork, should have a 

 diameter of not more than 7 or 8 mm. Steam is kept constantly in the boiler, and 

 connection with the receiver is made or broken instantly by inserting or removing the 

 cork. The most convenient support for the receiver, whether it be used in or out of 

 the laboratory, is an ordinary tumbler or drinking glass. The tube rests on a piece of 

 cork, grooved to take the bend of the tube, and it is steadied by a ring made of a piece 

 of india-rubber tubing. This form of support has many advantages. In the first 

 place, the apparatus has great stability ; then the glass is transparent, and it is essential 

 to be able to see the boiling mixture during the whole course of the experiment ; also, 

 while being transparent, the glass protects the receiver from excessive loss of heat. 



In the experiments to be reported, the principal thing to be observed is the differ- 

 ence between the temperature of pure saturated steam and the temperature produced 

 by the condensation of this steam in the mixture of salt and brine. It is, therefore, of 

 equal importance to observe accurately the temperature of pure saturated steam as to 

 observe that of the boiling mixture. The same apparatus suffices for both purposes. 

 Before charging, and being clean and dry, the receiver is connected with the boiler, and 

 >team blown through it. Some of it condenses and collects at the bottom of the 

 eceiver, forming a pool of distilled water boiled by steam, the steam produced by which 

 s perfect for the purpose. As the division marking 100° C. is usually some way down 



