Another very simple condenser is shown in Fig. 12, which will readily explain itself. The oast-iron exit pipe from each cylinder is carried through a separate tank, or long box, about 30 ft. long by 3 ft. square, and dips into a spout at -the end through a reduced pipe. The tank is kept full of constantly renewed water. Condensation by this method is not very perfect, and the great length of pipe renders proper cleaning out difficult. The uncondensed gases are carried off by a small pipe.
The plan which seems the most convenient, but which is not very largely used, is shown in Fig. 13. The exit pipe from the ovens, reduced in size to about 6 in., is connected with a range of pipes, preferably of copper, set zigzag fashion iu an upright, strong, wood framework. By means of an overhead pipe, which is perforated on its under side, a constant flow of water is precipitated over the whole range along which the gaseous and half-condensed products of distillation are passing, and falls into a tank in which the framework is set. A small pipe carries off the uncon densable gases to be consumed in the retort fire. All the ends of the condenser pipes should be closed by blank flanges, so that there may be no difficulty in cleaning out the tarry deposit. What ever form of condenser is used, the exit pipe from the oven should be connected with it by means of a short length, as shown in Plate I., so that the apparatus can be readily and quickly dis connected. For eeonerny's sake, two ovens are sometimes mado to work through one set of con densing pipes, but much better, and more certain, results are obtained when each oven has its separate condenser.
The condensed products consist of water, pyroligneous acid, ammonia, tar, naphtha, and various oils and resinous matter ; the un condensable gases, returned to the fireplace or allowed to pass off into the air, consist of carbonic oxide, carbonic acid, marsh, and olefiaut gases. The former aro delivered into a tank, where the tar settles to the bottom and is drawn off by stop-eoeks to the still, and the supernatant liquor — consisting chiefly of water, pyroligneous acid, and naphtha, with a certain admix ture of tarry impurities—runs over, or is drawn off into a smaller re eeptaele, from whence it is pumped into the neutralizer. This neu tralize• should be set on a higher level, that no further pumping, to the end of the aeetato of lime process, may he neeessary.
Returning for a mo ment to the first receiving tank into whieh the whole of the liquors from the condensers pass, a con venient form is shown in Fig. 14. A tank shut 20 ft. long, 5 ft. deep. and 5 ft. wide, built of
perfectly sound deals, which should be not less tl,an 3 in. thick, without cracks, and firmly bolted together with 1-in. iron rods, is divided into three compartments, the divisions having a slight depression to allow the liquor to flow from one compartment when filled into the next, and so on till it finally flows over into the pumping well. The tar is deposited in the several compartments, and is drawn off for distillation. The products of distillation may be returned into the spout leading from the condensers. Very often, however, it is not deemed advisable to purify the tar in any way, and tho whole of it is burned for fuel—mixed with sawdust, &e.—or is used for various purposes in the works. The lighter tarry and carbonaceous matters which rise to the surface as a scum, while the liquors are passing through the various tanks, are skimmed off and utilized as fuel.
If it be desired to obtain the pyroligneous acid by itself, or if a grey or white acetate of lime is required, the liquors from the tar settlers are distilled at a gentle heat, the naphtha passing over first, and the less volatile exude acid, mixed with various tarry and oily impurities, remaining in the still to be obtained by subsequent distillation. If it is only necessary to produce a brown acetate, the liquors are pumped up and mixed with lime in the neutralizer, as aforesaid, and the naphtha separated by after-distillation. A well-ordered works will have the necessary plant for both brown and grey acetate, so that command of more than one market for the absorption of the finished article may be obtained. For further details of these processes see " Lime, Acetate of." Such is the manufacture of crude pyroligneous acid as earried on at an ordinarily-well con structed English works, and the process itself leaves eomparatively little to be desired in the way of improvement. Manufacturers should, however, turn their attention to the better separation and utilization of the tar products and constituents, the utilization of the waste gases and the refuse from tho neutralizers, and the direct purification of the crude acid. It would probably pay well, too, to establish small turneries in the works to use up the odds and ends of timher now wasted, or only used for fuel.