If we attempt to change either the temperature or the pressure ice will melt, water will evaporate or vapour condense until one or other of the phases has vanished.
The perennial lakes, such as those just described, hold their waters for years and perhaps centuries; but the ephemeral lakes usually evaporate in the course of the summer.
The former, if it existed at all, could be found only in the more depressed portions; and even here it would evaporate under the influence of the sun's rays, forming a vapour which, if it existed in considerable quantity, would in some way make itself known to our scrutiny.
If the violet solution is allowed to evaporate slowly at ordinary temperatures the sulphate crystallizes out as Cr2(S04)3.15H20, but the green solution on evaporation leaves only an amorphous mass.
Another method, which is suitable for volatile liquids or low temperatures, is to allow the liquid to evaporate in a calorimeter, and to measure the quantity of heat required for the evaporation of the liquid at the temperature of the calorimeter and at saturation-pressure.
The wine, however, contains alcohol and water, both of which evaporate, but the alcohol faster than the water, so that the superficial layer becomes more watery.
Nearly all lead ores contain more or less sulphur; and as in the process of solution in nitric acid this is oxidized to sulphuric acid which unites with the lead to form the very insoluble lead sulphate, it is simpler to add sulphuric acid to convert all the lead into sulphate and then evaporate until the nitric acid is expelled.
It does not evaporate or turn rancid, whilst its marked hygroscopic action ensures the moistness and softness of any surface that it covers.
Hence if two vessels, one filled with solvent and one with solution, be placed side by side in an exhausted chamber, vapour will evaporate from the solvent and condense on the solution.
Externally chloroforrr ‘ is an antiseptic, a local anaesthetic if allowed to evaporate, and a rubefacient, causing the vessels of the skin to dilate, if rubbed in.
It was found that the method yielding the best results was to make incisions in the poppy-heads soon after sunrise, to collect the juice with the finger immediately after incision and evaporate it as speedily as possible, the colour of the opium being lighter and the percentage of morphia greater than when the juice was allowed to dry on the plant.
In the puszta are numerous small lakes, named generally Feher To or White Lakes, because they evaporate in the summer leaving a white crust of soda on their bed.
Dissolves the most uncrystallizable in preference to that which is most crystallizable sugar," and the patentee speaks of " a discovery I have made that no solution, unless highly concentrated, of sugar in water can without material injury to its colouring-and crystallizing power, or to both, be exposed to its boiling temperature during the period required to evaporate such solution to the crystallizing point."
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 fact that sea-water does evaporate more slowly than fresh water has been proved by the observations of Mazelle at Triest and of Okado in Azino (Japan).
For example, a factory able to evaporate 622 tons of water in 24 hours could treat I 000 tons of canes yielding juice of 9° B., and make therefrom too tons of sugar in that time; but this same factory, if supplied with canes giving juice of 6° B., could not treat more than 935 tons of canes in 24 hours, and would only make therefrom 62.2 tons of sugar.
It is unquestionably better and easier to evaporate in vacuo than in an open pan, and with a better system of firing, a more liberal provision of steam generators, and multiple-effect evaporators of improved construction, a far larger yield of sugar is obtained from the juice than was possible of attainment in those days, and the megass often suffices as fuel for the crop.
The total heat of the saturated vapour at any temperature is usually defined as the quantity of heat required to raise unit mass of the liquid from any convenient zero up to the temperature considered, and then to evaporate it at that temperature under the constant pressure of saturation.
" What the author was, his book, in spite of himself, tells us to some extent: a Christian of Judeo-Alexandrine formation; a believer without, apparently, any personal reminiscence of what had actually been the life, preaching and death of Jesus; a theologian far removed from every historical preoccupation, though he retains certain principal facts of tradition without which Christianity would evaporate into pure ideas; and a seer who has lived the Gospel which he propounds."