|28 ON A PROCESS OF FRACTIONAL CONDENSATION. 



except that they required too frequent renewal. I have found the cloth covered 

 •with vulcanized caoutchouc preferable to the common caoutchouc tubing. In the 

 smaller sizes of apparatus I have the end of the worm itself project far enough from 

 the bath to connect directly with the retort by means of a perforated cork, without 

 the use of an additional connecting tube. 



The upper end, h, of the elevated worm is brought out through the side of the bath 

 at a point about three inches below the top ; so that, when working with a low tem- 

 perature of the bath, the worm may still be completely covered with oil, and also give 

 sufficient space above the worm for the expansion of the oil when higher tempera- 

 tures are employed. To avoid contaminating the atmosphere of the laboratory with 

 the disagreeable fumes which are given off, in large quantity, from such a mass of 

 heated oil, the top of the bath is tightly closed with a sheet-iron cover, from which a 

 small funnel, a, Fig. 1, conducts these fumes to a chimney. 



In the larger apparatus, the vapors which succeed in passing through the heated 

 worm are conducted downward into a cooled worm contained in a bath of water, ii, 

 Fig. 2, and the liquid product is collected in the receiver, Jc. The cold bath, ii, contains 

 two condensing worms, — one for each apparatus, — and is large enough to condense 

 for both without the necessity of renewing the water. I have represented two appa- 

 ratuses combined, as it will be found more economical of time to operate with two at 

 once. In the smaller apparatus, for the table, a Liebig condenser may be conveniently 

 substituted for the cold worm, as shown in Fig. 1. 



For collecting liquids which boil below the common temperature, when such are 

 present, I attach a refrigerator, b, Fig. 2, which is provided with two block-tin con- 



densing-tubes, — one for each apparatus. These are bent in a zigzag form, and 



attached to the inner sides of the refrigerator. The lower ends of the tubes extend 

 through the end of the refrigerator far enough to form a convenient connection with 

 the second receiver, /, Fig. 2, which communicates with the first receiver, Jc, by means 

 of the glass tube, m. 



In order to successfully collect and condense the vapors of such extremely volatile 

 liquids as are now under consideration, it is of course indispensable that the apparatus 

 should be constructed with very tight joints ; and for greater convenience, but more 

 especially to prevent breakage, such of the joints as require to be frequently taken 

 apart should be made flexible. A very convenient and perfectly tight joint of this 

 kind may be made as follows : — the short stationary tube, n, in the cork of the 

 receiver, k, Fig. 2, is made with the opening somewhat divergent upward ; the end, o, 

 of the worm is enough smaller than the inside diameter of the upper end of the tube, 



