The liquid is then evaporated under a vacuum of 27 to 28 in.
There is no such thing really as a vacuum, any more than there are atoms or ultimate indivisible particles.
Her English vocabulary was growing a word at a time—mostly terms like dust, vacuum, linens, dishes and other domestic terminologies.
The exhaust steam passing from the engine through the blastpipe and the chimney produces a diminution of pressure, or partial vacuum, in the smoke-box roughly proportional to the weight of steam discharged per unit of time.
Evaporation and subsequent distillation under a high vacuum gives crude glycerin.
Of mercury, and, when of specific gravity 1.295 (corresponding to about 80% of glycerin), it is distilled under a vacuum of 28 to 29 in.
The steam is introduced into the pipes at about the pressure of the atmosphere, and is sucked through the system by means of a vacuum pump, which at the same operation frees the pipes from air and from condensation water.
For the production of high vacua, see Vacuum Tube; Liquid Gases.
- Telluriumbismuth Vacuum Thermal Detector for Electric Oscillations.
On other estates the second sugars, or sugars produced from boiling molasses alone, are not purged to dryness, but when sufficiently separated from their mother-liquor are mixed with the defecated juice, thereby increasing its saccharine richness, and after being converted into syrup in the usual manner are treated in the vacuum pan as first sugars, which in fact they really are.
About the same time Davy showed that two pieces of ice could be melted by rubbing them together in a vacuum, although everything surrounding them was at a temperature below the freezing point.
There is this difference, however, between this experiment and the operation imagined by Maxwell, that when the gases have diffused the experiment cannot be repeated; and it is no more contrary to the dissipation of energy than is the fact that work may be derived at the expense of heat when a gas expands into a vacuum, for the working substance is not finally restored to its original condition; while Maxwell's "demons" may operate without limit.
In that most largely used, known as " creosoting," dead oil of tar, to the amount of some 3 gallons per sleeper, is forced into the wood under pressure, or is sucked in by vacuum, both the timber and the oil being heated.
Thick, of which one end was kept at too° C., the rest of the rod in a "vacuum" (of 5 mm.
Thus, supposing that moo lb of coal were required to work a single vacuum pan, evaporating, say, 6000 lb of water in a given time, then 500 lb of coal would be required for a double-effect apparatus to do the same work, 333 lb for a triple effect, 250 for a quadruple effect, and 200 lb for a quintuple effect.
Today, she'd give anything just to have Ashley back, no matter how long it took her to fix the vacuum cleaner after it choked on the beads.
On raising the piston, the valve F remains closed and a vacuum tends to be created in the cylinder, but the pressure of the atmosphere forces the liquid up the tube D and it raises the valve E and passes into the cylinder.
It is found that in reducing the juice of these two qualities to syrup, fit to pass to the vacuum pans for cooking to crystals, the total amount of evaporation from the degraded j uice is about half that required from the normal juice produced by double crushing.
The defecated cane juice, having lost about 70% of its bulk by evaporation in the multipleeffect evaporator, is now syrup, and ready to enter the vacuum pan for further concentration and crystallizaHoward's tion.
Since Howard published his invention the vacuum pan has been greatly improved and altered in shape and power, and especially of recent years, and the advantages of concentrating in vacuo having been acknowledged, the system has been adopted in many other industries, and crowds of inventors have turned their attention to the principle.
The " minus pressure " steam system, sometimes termed " atmospheric " or " vacuum," is of more recent introduction than those just described.
The coagulated rubber separated from the watery fluid is cut up into small pieces and passed through the grooved rollers of the washing machine, from which it issues in sheets, long crinkled ribbons or " crepe," which are then dried in hot air chambers or in a vacuum dryer, by which means the water is dissipated at a lower temperature.
It is a white solid, fusing at 250° C. to an oily liquid which boils at 606°, and volatilizing at a red heat in nitrogen, a vacuum or hydrochloric acid, without decomposition.
This weak solution, called " sweet water," is sometimes used for melting the raw sugar, or it is evaporated in a multiple-effect apparatus to 27° Beaume density, passed through the char filter, and cooked in the vacuum pan like the other liquors.
During the returnstroke the latter was kept closed in virtue of the partial vacuum formed within the cylinder, while at the same time the former n'as forced open by the pressure of the denser air in the vessel and nozzle.
(I) The principle is illustrated in the article Barometer, where a column of mercury of density a and height h, rising in the tube to the To:ricellian vacuum, is balanced by a column of air of density p, which may be supposed to rise as a homogeneous fluid to a height k, called the height of the homogeneous atmosphere.
He was resigned to quietly reading a book until Mrs. Porter the housekeeper showed up a day early, accommodating a family wedding, and Dean's peace began competing with the sounds of a vacuum cleaner and Mrs. Porter's radio music, even worse junk than Fred's usual selections.
As the indicated horse-power of the engine increases, the weight of steam discharged increases, and the smoke-Lox vacuum is increased, thereby causing more air to flow through the furnace and increasing the rate of combustion.
The impure glycerin obtained as above is purified by redistillation in steam and evaporation in vacuum pans.
While determining its atomic weight, he thought it desirable, for the sake of accuracy, to weigh it in a vacuum, and even in these circumstances he found that the balance behaved in an anomalous manner, the metal appearing to be heavier when cold than when hot.
(26) Also A = B = H H4?rI _ I +41K, (27) and (28) 471 Since in empty space B has been assumed to be numerically equal to H, it follows that the permeability of a vacuum is equal to i.
From the equation K=(µ - I)/47r, it follows that the magnetic susceptibility of a vacuum (where µ = I) is o, that of a diamagnetic substance (where, u < I) has a negative value, while the susceptibility of paramagnetic and ferromagnetic substances (for which µ> I) is positive.
The gaseous mixture obtained by burning guncotton in a vacuum vessel contains steam, carbon monoxide, carbon dioxide, nitrogen, nitric oxide, and methane.
When slowly heated in a vacuum vessel until ignition takes place, some nitrogen dioxide, N02, is also produced.
An absolute vacuum cannot be produced on account of the unavoidable air-film between the mercury and the walls of the apparatus.
The clear juice when it arrives at the top of the separator flows slowly over the level edges of, a cross canal and passes in a continuous stream to the service tanks of the evaporators or vacuum pan.
After the juice has been defecated or purified by any of the means above mentioned it is sent to the evaporating apparatus, hereinafter described, where it is concentrated to 26° or 28° Beaume, and is then conducted in a continuous stream either into the service tanks of the vacuum pan, if dark sugars are required, or, if a better colour is wanted, into clarifiers.
The latter are circular or rectangular vessels, holding from 500 to 1500 gallons each, according to the capacity of the factory, and fitted with steam coils at the bottom and skimming troughs at the top. In them the syrup is quickly brought up to the boil and skimmed for about five minutes, when it is run off to the service tanks of the vacuum pans.
The heat at which the syrup boils in the clarifiers, 220° F., has the property of separating a great deal of the gum still remaining in it, and thus cleansing the solution of sugar and water for crystallization in the vacuum pans; and if after skimming the syrup is run into separators or subsiders of any description, and allowed to settle down and cool before being drawn into the vacuum pan for crystallization, this cleansing process will be more thorough and the quality of the final product will be improved.
With open-fire batteries for making the syrup, which was afterwards finished in the vacuum pan, very good sugar was produced, but at a cost that would be ruinous in to-day's markets.
But this competition among inventors, whatever the incentive, has not been without benefit, because to-day, by means of very simple improvements in details, such as the addition of circulators and increased area of connexions, what may be taken to be the standard type of multiple-effect evaporator (that is to say, vertical vacuum pans fitted with vertical heating tubes, through which passes the liquor to be treated, and outside of which the steam or vapour circulates) evaporates nearly double the quantity of water per square foot of heating surface per hour which was evaporated by apparatus in use so recently as 1885 - and this without any increase in the steam pressure.
So also the principles laid down by Howard with respect to the vacuum pan hold good to-day: larger pans have been made and their heating surface has been increased, but it has been found by practice now, as it was found then, that an ordinary worm or coil 4 in.
Thus the most efficient vacuum pans of the present day are those which have their coils so arranged that no portion of them exceeds 50 or 60 ft.
In certain districts, notably in the Straits Settlements, syrup is prepared as described above for crystallization in a vacuum pan, but instead of being cooked in vacuo it is slowly boiled up in open double-bottom pans.
When Cuba was the chief sugar-producing country making clayed sugars it was the custom (followed in refineries and found advantageous in general practice) to discharge the strike of crystallized sugar from the vacuum pan into a receiver heated below by steam, and to stir the mass for a certain time, and then distribute it into the moulds in which it was afterwards clayed.
Some crystallizers are made entirely cylindrical, and are connected to the condenser of the vacuum pan; in order to maintain a partial vacuum in them, some are fitted with cold-water pipes to cool them and with steam pipes to heat them, and some are left open to the atmosphere at the top. But the efficiency of all depends on the process of almost imperceptible yet continuous evaporation and the methodical addition of syrup, and not on the idiosyncrasies of the experts who manage them; and there is no doubt that in large commercial processes of manufacture the simpler the apparatus used for obtaining a desired result, and the more easily it is understood, the better it will be for the manufacturer.
The clear juice thus obtained is evaporated in a multiple-effect evaporator and crystallized in a vacuum pan, and the sugar is purged in centrifugals.
An economical method of evaporation must be found.
The vacuum pan is erected at a height which commands the crystallizers, each of which will, as in days gone by in Cuba, hold the contents of the pan, and these in their turn are set high enough to allow the charge to fall into the feeding-trough of the centrifugals, thus obviating the necessity of any labour to remove the raw sugar from the time it leaves the vacuum pan to the time it falls into the centrifugals.
By repeated fractionations he was able to divide yttrium into distinct portions which gave different spectra when exposed in a high vacuum to the spark from an induction coil.
All their endeavours have obtained at best but a doubtful success, for they have overlooked the fact that to evaporate a given weight of water from the syrup in a vacuum pan at least an equal weight (or in practice about 15% more) of steam must be condensed, and the first cost of mechanical agitators, together with the expenditure they involve for motive power and maintenance, must be put against the slight saving in the heating surface effected by their employment.
The crystallized sugar from the vacuum pan has now to be separated from the molasses or mother-liquor surrounding the crystals.
Briefly, sugar-refining consists of melting raw or unrefined sugar with water into a syrup of 27° to 28° Beaume, or 1230 specific gravity, passing it through filtering cloth to remove the sand and other matters in mechanical suspension, and then through animal charcoal to remove all traces of colouring matter and lime, thus producing a perfectly clear white syrup, which, cooked in the vacuum pan and crystallized, becomes the refined sugar of commerce.
On the other hand, the advocates of admitting the feed into a vacuum pan in many minute streams appeal rather to the ignorant and incompetent sugarboiler than to a man who, knowing his business thoroughly, will boil 150 tons of hot raw sugar in a pan in a few hours, feeding it through a single pipe and valve io in.
When this is the case the amplitude of the potential difference of the surfaces of the tubular condenser becomes a maximum, and this is indicated by connecting a vacuum tube filled with neon to the surfaces of the condenser.
This liquid is concentrated in vacuum pans to a specific gravity of 40° to 44° B., a small quantity of sodium bisulphite solution being added to bleach it, to prevent fermentation, and to inhibit browning.