The cover i (Fig. 81) of the boiler is now put on, and the flask is left in for 20 minutes, the cover being removed every 6-7 minutes, so the flask may be shaken each time for 20-30 seconds during the 20 minutes the emulsion has to boil.
The flask is next removed from the boiler, and the emulsion is poured from it into a quart stone bottle (an ordinary stone porter bottle will answer); the flask is immediately rinsed with 20 cc. of distilled warm water, and the latter is added to the emulsion in the stone bottle. The bottle is corked and put under a stream of cool water until the temperature of the emulsion is reduced to 85°-90° F., but it must not exceed 90° F.
After the emulsion has cooled down to 85°-90° F., the bottle is removed and the following solution -
Alcohol.. ...... 5 cc.
Ammonia (sp. gr. 910) 105 m: is added, a little at a time, vigorously stirred, the bottle being shaken up after each addition.
The water in the boiler. f (Fig. 81) must not now be warmer than 100° F., and after putting in the bottle, which must be nearly covered with the water, the gas flame should be turned down law.
It will now be necessary to tie the cork down, else it will be liable to be forced out, thereby damaging the emulsion, for we may now remove the lamp from the lantern and work by a strong light. The bottle is now replaced in the boiler f, the water in which must be kept at a temperature of 100° F., and the bottle allowed to remain there 30 minutes. The light below is next extinguished, and the bottle is kept in the boiler till the next morning. It is then removed and vigorously shaken for 2-3 minutes. This should be repeatel 7 or 8 times for a period of 12 hours.
During the day, while away from home, have some one at home to do the shaking. Returning in the evening, prepare No. 3 solution in a 12 oz. glass beaker, setting it into a water bath at a temperature of 125° F., and while preparing the above and dissolving it, the bottle of emulsion is also set into another water bath, at a temperature of 90° F. When No. 3 solution is dissolved, it is cooled down to 100° F„ and added, 2 oz. at a time, to the warm emulsion in the stone bottle, the latter being well shaken after each addition. This must be done by ruby light. .
As soon as all of No. 3 has been added, the bottle is well shaken, and the emulsion is poured into a 2 lb. gallipot (an article which can be obtained from almost any druggist); the cover is put on, and it is left standing for 10 hours, or until the next morning, when it will have solidified into the form of a jelly. To remove it from the pot, pour in upon the jelly a few ounces of water ,* then with a glass rod loosen the cake of jelly from the inside by running the rod around between the jelly and the interior surface of the pot. When the pot is turned over, the emulsion jelly comes out in one cake and falls into the well, a, of the squeezing press, Fig. 83, falling on a silver plated copper wire net b at the bottom (see the full size of the meshes in Fig. 85). By means of this press the emulsion is forced through the netting into the washing wood bucket c below (see terior of the washing box a. Fig. 88, and in one side of the latter is a siphon tube b. The stratom of emulsion seen in the bottom of the bucket c (Fig. 88) is washed for en hour or more by allowing the water to enter from above in a gentle stream, about as fast as the siphon draws it off. By stopping the inflow the siphon will drain out all the water.
The cover d of the washing box has a conical-shaped aperture in the top Tor the rubber cork holding the inlet tube; when this tubs and cork are withdrawn, the extra cork e, hanging by a string at the side, is put in. f is a sink placed near the table for carrying off the waste water. The washed emulsion should now be tested for fog, which is done by taking two 3 oz- beakers, putting into one 1 oz. of developer prepared for developing a plate, and in the other 1 bz.
With a silver spoon, a small quantity the bucket c and dropped into each of the beakers. If it is a pyro developer, it is allowed to stand for two minutes; if ferrous oxalate, 5 minutes; then the developer is thrown off and the emulsion is rinsed in three changes of distilled water, and both samples, the one that had the developer on end the one without, are taken as soon as possible to daylight and compared; if this is not done promptly, they will change colour very quickly, if the emulsion that had the developer on does not look in any way blackish, or show any change, it proves that it is perfect, and will do to coat plates with. If, on the other hand, there is a perceptible difference in colour between the two. it will be a sure sign that the emulsion is defective, and the quickest way to dispose of it will be to throw it into the waste and prepare afresh another batch.
If the emulsion is right, it is left to drain in the bucket for 8-9 hours, or from morning to night, then the backet is removed and placed upon 5 or 6 sheets of thick blotting paper, previously soaked in 4 or 5 changes of hot water and after-wards dried to Res it of hypo. The netting at the bottom of the basket comes directly in contact with the paper, and as soon as a sheet is wet it is removed and replaced with a fresh one. The emulsion is worked over with a silver spoon, bo as to bring new surfaces toward the blotters.
After all the water has been absorbed, the emulsion is transferred from the bucket to the gallipot (which jo the meantime has been very well cleaned) and is melted by immersing the pot in a water bath having a temperature of 135° P.; 20 cc. of alcohol are now added to the emulsion, and as soon as it is melted it should be filtered as shown in Fig. 86, through Canton flannel, with the smooth side outward or against the glass of the funnel, and elevated from the surface of the funnel in convolutions or folds by atrip of glass a, 1/2 in. wide. In Fig. 87, the funnel a is set into a funnel-shaped receptacle or seat formed of tin in the interior of the water bath of 130° F. c represents an inlet tube for water, and d is an outlet tubs for steam, e is a cork at the bottom of the bath, by which it can be readily emptied. Below the bath b is a metal vessel f inclosing an earthen tea-pot g, which is set just under the tube of the funnel and receives the filtered, emulsion, It usually takes about 10 minutes for 22 oz. of emulsion to filter through.