Compared with a Liebig condenser of similar dimensions, this apparatus exposes probably 3 times as much condensing surface. The idea of a tubular con-forth, is, in the opinion of the American Journal of Pharmacy, an excellent one, that may find useful imitation in the chemical laboratory and elsewhere. The device illustrated and described was invented by Joseph P. Remington, whose recommendation of its merits is based upon a continuous use of it for 3 years.
In chemical or pharmaceutical operations, it often becomes necessary, after having used an upright condenser for the purpose of continuous extraction, to reverse the whole condenser, in order to recover the volatile menstruum. This also necessitates, in most cases, a change of the current of water for cooling the apparatus. All this may be avoided by constructing the condensing tube in the manner shown in Fig. 102. From a bulbous expansion blown in the tube at its lower end, a tube c arises, provided with a faucet d, and subsequently turned-at a right angle downwards. At about the centre between the faucet and the angle, the glass tube passes through a support connected with the condenser, whereby it is in a great measure protected from being broken off. The use of this modified condenser is almost self-evident. If it is used for continuous extraction, so that the condensed liquid constantly flows back into the flask connected with a, the faucet at d is closed. The condensed liquid will then at first fill the tube c until it flows over into the tube a. Finally, when the operation is to be finished, a receiver is placed under e, and the faucet is opened, when all the condensed liquid may be collected without disturbing the connections of the condenser.
It is advisable before opening the faucet d to dip the end of the tube e into a flask containing a portion of the liquid which is to be distilled over, f. i. ether. The depth to which the Cube may be dipped should be less than the length of the column of liquid contained between c and d. (Simand.)
Dr. Carl Roth draws attention to a condenser lately devised by him. He was led to its construction by the frequent breaking of the tubes in Liebig and Hoffmann condensers, in which latter the water immediately surrounds the tube containing the vapour. While, ordinarily, there is little danger of the tubes bursting, they are, nevertheless, quite liable to do so in cases of the distillation of absorption products.
Dr. Roth's condenser, as Fig. 103 shows, consists of a glass tube around which is wound a thin leaden pipe of 10-15 times the length of the glass. The pipe is first wound with the convolutions close together, and is then brought back in large turns. This arrangement allows the water to be heated somewhat before it gets close to the glass, and in addition it utilises to a greater extent than in the old form. Its efficiency can be increased still more by placing tinfoil upon the glass before winding the tube. Another advantage of the apparatus is, that in case the glass tube bursts, the distillate will not be in danger of becoming mixed with water.
Dr. Roth states that he has used this form successfully in experiments that would inevitably have caused the destruction of Liebig's condenser. In the figure the water enters at a and flows out at b. (Din7. Pol, Jl.)
The stills which are used by pharmaceutists or chemists are usually provided with a head terminating in a tapering pipe, which is intended to be conneeted to the worm or condenser. This connection, however, is, in many cases, quite awkward, and often a source of loss from leakage. Those who hare had much occasion to work with such an apparatus will fully appreciate the truth of this. In large stationary at ills, used on a manufacturing scale, the condenser consists of several parts; the so-called column, a series of vessels, which the vapours have to traverse, and in which all that part of the vapour condensable below a certain temperature is reduced to the liquid condition, and returned to the still; and in addition to this a regular worm or condensing cooler. Such arrangements are, however, too circumstantial for small stills.
To obviate the difficulties above mentioned, Rice has constructed a new form of still-bead and condenser, which completely answers all demands made upon it. It requires one packing, may be used as a reflux-condenser, and saves a great deal of room, from the fact that a special worm-tub is made unnecessary. Fig. 104 gives a correct representation of the apparatus.
It consists mainly of 2 parts; the still and the bead with condenser. The still has a capacity of 16 gal., and is heated by steam, which enters at o, b being the exhausting pipe. The still-head is constructed of tolerably heavy copper, to be able to bear the weight of the condenser, which is fastened to it by 3 iron legs, attached with rivets, The condenser is a cylindrical copper vessel, of the capacity of about 10 gal., with rounded bottom and closed top, having short 1/2-in. tubes projecting from the bottom and from the top - at c and d. There are 2 such tubes at the bottom, one for attaching the rubber nose e bringing the water; the other, shown in the cut immediately alongside the letter c, is closed with a cork, and is used to permit the water to be emptied without detaching the hose from the other. At the top there are likewise 2 tubes, one at d, for attaching rubber hose to carry off the water into the waste-pipe f; the other, being closed with a cork, is not shown in the cat, as it is on the back of the cona uniform downward descent throughout. After emerging from the condenser at i, it extends for a short distance, where the cut shows it to be connected to the separate block-tin pipe k by means of a union joint lined with tin.