Emulsion

“ The ideal emulsion for the damping agent is olive oil and soft soap heated and mixed together to form an emulsion, but the high cost of these commodities have placed them out of the reach of practical work and now various substitutes are employed. ”

“ We can put these emulsion plates and carry them off where we please, and, what is still more important, we can put the emulsion upon very thin material, and I have here (exhibiting them) thin sheets of celluloid upon which this emulsion has been spread and pictures taken. That is not all, either; they can make it still thinner (producing small camera) they can put it on a roll and in this camera is one of those rolls, and in that box I can take a hundred pictures without reloading the instrument. ”

“ This sort of oily liquor, in which the oil is only divided, not dissolved, is called an Emulsion. The oily particles in Emulsions spontaneously separate from the water, when left at rest, and uniting into greater masses rise, on account of their lightness, to the surface of the liquor, which by that means recovers a degree of transparency.
If vegetables abounding in essential oils and resins be digested in spirit of wine, the menstruum takes up these oily matters, as being capable of dissolving them ”

“ A very excellent method of preparing an orthochromatic collodion emulsion has been described by Hübl,2 which can be used either wet or dry. Repeated trials made in the Imperial Military Geographical Institute, in our establishment, and in the Photographic Institute in Vienna have proved the advantageous use of this method for orthochromatic work. The raw emulsion, according to Hübl, is prepared as follows:—40 g. of silver nitrate are dissolved in 50 ccm. of warm distilled water, and as much ammonia added as will give a clear solution; then 100 ccm. ”

“ Vogel has recently introduced an emulsion made with acetic acid, gelatine, pyroxyline, and bromide of silver, which is very clean and very fairly rapid. Plates are more readily coated with it than with gelatine emulsion, but less so than with collodion emulsion.
Another very decided advance in photography is the doing away with glass as a support for the emulsion. Mr. Warnerke has perfected a process by which the photograph is taken on paper instead of on glass. He has a sensitive tissue which can be made of any length, and can be rolled on a roller and exposed in the dark slide. ”

“ Experiments by Hillyer (loc. cit.) show, however, that while N/10 solution of alkali will readily emulsify a cotton-seed oil containing free acidity, no emulsion is produced with an oil from which all the acidity has been removed, or with kerosene, whereas a N/10 solution of sodium oleate will readily give an emulsion with either, thus proving that the emulsification is due to the soap itself, and not to the alkali. ”

“ In about 1870 it was conceived that you could make an emulsion of these peculiar compounds of silver—these sensitive silver compounds—that you could make an emulsion that you could pour upon the plate and produce a picture just when you pleased, and it was found that by mixing the chloride that produces the sensitive material in one portion of your collodion and putting nitrate of silver into another portion of the collodion, in certain proportions, you could produce a collodial emulsion. ”

“ By forcing 51melted butter-fat or oil mixed with water or skim milk through exceedingly small apertures under high pressure, or otherwise breaking up the mixture, an emulsion can be formed in which the fat globules are much finer even than those in natural milk or cream, and separation can be prevented. The force used in these emulsifiers may be produced by powerful pumps, or a steam jet, or centrifugal force under high speed; whichever system is used the machines answer the same purpose, to produce a permanent emulsion in which the oil or fat will stay in suspension even after cooling. ”

“ The previously-formed saponaceous mixture is now to be placed in the mortar, and the ready-formed emulsion in the runner; the soapy compound and the emulsion is then carefully blended together. As the last of the emulsion runs into the mortar, the spirit, in which the otto of roses has been dissolved, is to take its place, and to be gradually trickled into the other ingredients. A too sudden addition of the spirit frequently coagulates the milk and causes it to be curdled; as it is, the temperature of the mixture rises, and every means must be taken to keep it down ”

“ This emulsion-like mass is brought on to the paper by the machine, not the ink alone, as in collotype, the chromated film of which holds only that moisture which is requisite for its swelling, while its support, the glass, can retain no moisture. It is also the fact that the amount of moisture in the collotype film is so small that the formation of this emulsion practically does not occur. From these comparisons and explanations it also follows that the printing technique of the two processes must differ. ”

“ We all know what an alarming quantity of silver seems to be going down the sink when we wash vessels to which a very small quantity of emulsion is adhering. If filtering be resorted to the liquid which comes through will be quite clear. This was somewhat unexpected by me, as, if an emulsion containing the whole of the gelatine be precipitated into alcohol in the usual way, the alcohol becomes milky with a substance which could not, I imagine, be filtered from it. ”

“ This extreme fineness is secured by long emulsification, or by the use of ammonia and a boiling heat.
The strength and tenacity of the emulsion depend on the quality of the gelatine, and its freedom from deterioration during the process of emulsification and the subsequent washing. A soft gelatine is suitable for the process of emulsification; afterwards a hard quality is used to give body and resistance.
The presence of free bromide or of free nitrate of silver in the finished emulsion would be fatal to its usefulness ”

“ On the first day of treatment small quantities of an emulsion of the cord exposed for thirteen or fourteen days in saline solution are injected subcutaneously, and the treatment is continued for from fifteen to twenty-one days, according to the severity of the bite, a stronger emulsion — i.e. an emulsion made of a cord that has been desiccated for a shorter period being used for each succeeding injection, until at last the patient is injected with an emulsion which has been exposed to the air for only three days. ”

“ These pumps draw the emulsion from a sufficient depth in the trough to avoid danger from the presence of air bubbles, and the bottom of the trough is so shaped that should by chance any sedimentary matter be present, it has a tendency to travel downward, away from the bottoms of the pumps. There is a steady flow of emulsion from the pumps to the delivery pipes, then it passes down a guide plate of the exact width of the plate to be coated. ”

“ The great advantages of this apparatus are as follows: 1. From the moment the lid is closed one can work by daylight. 2. The method of washing in moving water is combined with that of complete change of water. 3. The emulsion never comes in contact with metal. 4. Whoever wishes to prepare dry gelatine only requires, when the washing is over and the vessel perfectly emptied, to leave the emulsion to drip for a time, and then to lift out the sieve and its contents and place it in a suitable vessel with absolute alcohol. ”

“ He further, in August 1879, announced that he had obtained great rapidity by adding to the bromide emulsion a certain quantity of ammonia. This addition rapidly altered the silver bromide from its ordinary state to the green molecular condition referred to above. At this point we have the branching off of the gelatin emulsion process into two great divisions, viz. that in which rapidity was gained by long-continued heating, and the other in which it was gained by the use of ammonia—a subdivision which is maintained to the present day. ”

“ This method, although a great improvement upon the older ones, yet leaves much to be desired, especially for those who are not in the habit of making emulsion regularly, but only an occasional batch. When the weather is at all warm it takes a long time for the emulsion to set, unless ice be used, and when once it is set the washing process is an exceedingly "messy" one unless the water be cooled with ice; and the amount of water taken up during washing is often so great that there is considerable difficulty in getting the emulsion to set on the plates. ”

“ Fats are lighter than water, hence will float in it. An emulsion is a suspension of fat in a fluid, and the fat in this case must be very finely divided and mixed with some other material which will prevent a coalescence of the fat globules. In milk, which is one of the best natural emulsions, the additional substance is protein. ”

“ If Oil be mixed with water in a phial, and the mixture strongly shaken for some time, with a rapid and continued [Pg 393] motion, the Oil will be divided into a vast number of little globules, which intervening between the parts of the water will destroy its transparency, and give it a dead-white colour, like that of our Emulsion. ”

“ Spirit produces the same effect in those which are made with yolk or mucilage; and acids in those made with an alkali. The addition of these substances to emulsions should be therefore avoided as much as possible. Emulsions of wax, spermaceti, oil of turpentine, and balsam of copaiba, are the most readily and completely formed with yolk of egg. Volatile oils are more readily made into emulsions if mixed with an equal volume of some simple fixed oil, before proceeding to operate on them. Scammony is generally formed into an emulsion with milk; and resin of jalap, with almonds and water. ”

“ Moreover, the color does not again reappear after washing, as it does sometimes when the fixing salt has been partially washed away. In cases where there is great tendency to frill--such, for instance, as when a soft sample of gelatine has been employed, or old decomposed emulsion worked in with the fresh emulsion--it will in such cases be safer to put the plates in the normal-bath for a few minutes previous to immersing them in the acid bath. ”

“ Any person can try the experiment by first coating a plate in the ordinary way, and on the second plate just pour a small pool of emulsion on the center; let both dry, and he will then see after exposure which frills the easier on development. ”

“ The condition of close contact between cells and emulsion is achieved by the technique of dip-coating autoradiography. In this process the glass slide on which the cells are carried is dipped into a melted photographic emulsion (see Figure 15a) , a thin film of which clings to the slide. After it has been dried, the slide is placed in a lighttight box and kept in a refrigerator for the desired period of exposure, usually several days or weeks. ”

“ The yolk has an insipid, bland, oily taste; and, when agitated with water, forms a milky emulsion. If it is long boiled it becomes a granular, friable solid, yielding upon expression, a yellow, insipid, fixed oil. It consists, chemically, of water, oil, albumen, and gelatine. ”

“ One cubic centimeter intraperitoneal injections of the total resinous extract emulsion and the same amount of the iron acid emulsion were made into rabbits. During the three hours the animals were under observation no symptoms were produced. ”

“ A chief object of the machine is to deliver a carefully measured quantity of emulsion upon each plate, and this is done by means of pumps, in order that the quantity of emulsion delivered shall not be affected by changes in the level of the emulsion in the trough ”

“ The vapor plan is preferable in treating wet animal substances, such as offal; but for dry vegetable or animal matter—seeds, for instance, or the residuum resulting from the rendering of tallow—we prefer the plan before described.
The flooding or steeping of animal or vegetable matter in liquid hydrocarbon results in a mixture or emulsion of gelatinous, albuminous, and fatty or oily matter, combined with animal or vegetable tissues, the whole forming an amalgamated mass ”

“ This apparatus is principally valuable in dealing with large quantities, since it saves a great deal of labor, and affords perfect certainty of the emulsion being well washed. It may not be unnecessary to maintain that the difficulties of perfect washing--particularly if one do not wash with running water--increase at least in quadruple proportion to the quantity of emulsion manipulated.--Franz Stoke, Ph.D., in Br. ”

“ Bacterial Emulsion.—
1. Take an 18- to 24-hour culture of the required bacterium (e. g., Diplococcus pneumoniæ) grown upon sloped blood agar at 37° C. Pour over the surface of the medium some 5 c.c. of normal saline solution.
2. With a platinum loop emulsify the growth from the surface of the medium as evenly as possible in the saline solution.
3. Allow the tube to stand for a few minutes so that the large masses of growth may settle down; transfer the upper portion of the saline suspension to a centrifuge tube and centrifugalise thoroughly. ”

“ Scott's Emulsion.—This is a good emulsion of cod-liver oil, widely prescribed by physicians for the many patients who are too delicate-stomached to retain the [Pg 266] pure oil. For those who can take the refined oil straight, Peter Möller's brand is in a class by itself. ”

“ The oil is placed in a tank provided with an agitator. The latter is set in motion and the fatty oil or free fatty acid from which the soap is to be formed is added, and mixed intimately with the mineral oil. When the mixture is seen to be thoroughly homogeneous, the alkali, in solution in water, is added little by little and the stirring continued until a thorough emulsion is obtained, of which the constituents do not separate, even after prolonged standing at ordinary temperatures. The agitation may be produced either by a mechanical apparatus or by forcing air in under pressure. ”