Another improvement consists in mixing the pyroxyline and solvent, and combining the solution with oils and other matters, in a cylindrical vessel provided with a strainer' or filter at the lower end, through which the materials are made to pass when sufficiently mixed and dissolved. Fig. 475 shows a side view, partly in section, of such a vessel. A strong cylindrical vessel a is mounted on wheels b suitable for running on a light tramway, and fitted with a metallic bottom a' perforated with small holes and covered with fine wire gauze. The moist pyroxyline is first mixed roughly with the solvent and other liquid with which it is compounded, and the whole is placed in a. When there, the materials are thoroughly mixed and beaten together, by means of a mechanical beater ; this being completed, the mixing vessel is run into the press shown in side view in Fig. 476 :—a is the c3linder of the press ; b, the ram, on the head of which is a fran3e b', and within it enters the receiving can c. When the ram rises, it receives the lower eud of the mixing vessel d into a corresponding socket formed in it ; thus tbe mixing vessel is lifted to the piston e, which comes down upon the material in the former, and forces the whole of its contents, with the exception of the impurities, to pass through the perforated bottom into the receiving can c ; f is a projecting ring on the press head to prevent the ram rising too high.
Fig. 477 is a sido view of another mixing apparatus:—a a if3 the frame of the apparatus ; on it is mounted the axis b, which receives motion from a driving stmp ; b' ia a bevelled wheel, driving two bevelled pinions c and d, mounted on tubular axea, turning in bearings on the frame. Within the asia of the wheel c, is another tubular axia e, caused to revolve with it by meana of a groove and feather, and able to slide up and down vertically, through the axie of the wheel c ; e' e' ie a frame of beating bars fixed at the lower end of the axis e, and rotating with it ; f is another axia passing in a similar way through the axis e, turning within it, and capable of sliding up and down within it ; this axis passee down through the axis e, and carries, at ita lower end, the frame of beating bare f' f', which bars pass between the bare of the other frame e' as they revolve in opposite directions. The axes e and f are raised and lowered, ao as to lift them out of the mixing vesael, or lower them clown into it, by means of the hand wheel g mounted on the axis g' ; g" IS a apur wheel at the upper end of the axie g' ; it drivee another wheel h, mounted on a hollow axis carried by the frame. Thia axis has a ecrew thread cut in it corresponding with the acrew i, which worke within it ; the lower end of the screw embraces the head of the axis f ao as to cause it to rise and fall with it, but at the came time allowing it to rotate freely. In a similar way, the axle e at its upper end is made to embrace a collar on the axis f, ao that when the screw risea or falls, the axea e and f with the beating frames upon them go with it. This machine ia also very useful in mixing castor or other oil with chloride of aulphur, to produce a compound to be afterwarda mixed with the preparation of pyroxyline.
According to another plan, the pyroxyliue, having been dissolved and mixed with the other ingredients, is kneaded, and the excess of solvent and moisture is evaporated in an apparatua of the following description. The mixture is put into a box provided with an air-tight cover, and
containing a pair of rollers, which receive a rotary motion by suitable gearing on the out side. The axlea of the rollers enter the end of the box by air-tight joints ; they are hollow, and are arranged to admit of the paasage of steam or other fluid for heating the rollers. To this box or vessel there is a pipe attached, to convey off the vapour of the solvent. In order to induce the paseage of vapour from the box, a fau or exhausting apparatus is applied, which keeps up a partial vacuum, not only in the box, but also in the reaervoira containing the solvent, and in other parts of the apparatus connected with it. The vapour paseing off from the box is first conveyed into a chamber in which there ia a perforated partition, whereon chloride of calcium is placed ; through thia.the vapour risea, and any water ie thue separated from the vapour of the solvent, which pasaes away from the cylinder to a condenser. The vapour of the solvent, on being condensed, passes into a reservoir.
Fig. 478 is a plan, Fig. 479 a transverse section, and Fig. 480 a front view of the kneading apparatus :—cz is the frame ; on it is mounted a hopper b, into which the material is placed as it cornea from the prase ; at the bottom of the hopper ia a valve b', which can be opened by hand when desired, to allow material to descend from the hopper to the rollers c and d, which are made hollow and heated with steam internally ; the roller c is driven by the spur wheels c' and c", the latter of which it3 fixed on a main driving shaft ; c"' is a pinion at the further end of the roller c ; it gears with a pinion d' of larger size on the end of the roller d, so that the rollers c and d are driven at different epeeds, and have consequently a grinding action on the material passed between them; e is a casing surrounding the rollers ; it is furniahed with suitable doors, and is glazed at e' cc so that the workman rnay readily see what is going on within; e'' e" are apertures furnished with sleeves to allow the workman to introduce his arms within the casing e without causing any material escape of solvent vapour ; f f is a collecting knife, set up to the surface of the roller c by the adjusting screws f f' . The workman continually takes the material as it collects behind this knife, and passes it again between the rollers ; he also collects the rnaterial from the table g beneath the rollers, and passes it repeatedly through the rollers, until it is thoroughly blended, and the solvent is suf ficiently evaporated to bring it to the required consistence ; h is a pipe leading from the top and bottom of the easing, to conduct away any solvent or vapour of solvent which escapes from the mixture, to a cylinder containing chloride of calcium, and thence to a condensing ap paratus. A fan maintains a partial vacuum in the casing, drying cylinder, and condenser, and so draws the vapour through the apparatus. The chloride of calcium cylinder separates the vapour of water which results from the moisture in the pyroxyline, and the condenser retains the solvent and delivers it back into a suitable tank.