A cooling remedy for a feverish state.
The sun is thus slowly contracting; but as it contracts it gains heat by the operation of the law just referred to, and thus the further cooling and further contraction of the sun is protracted until the additional heat obtained is radiated away.
Causes an accumulation of air over the cold area, The diminution of barometric pressure which takes place all over Asia during the summer months, and the increase in the winter, are hence, no doubt, the results of the alternate heating and cooling of the air over the continent.
The evaporation from this large basin exercises a certain influence on the climate of the surrounding country, while the absorption of heat for the thawing of the ice has a notable cooling effect in early summer.
The heat at Damascus and Aleppo is great, the cooling winds being kept off by the mountains.
The frames into which hard soaps are ladled for cooling and solidification consist of rectangular boxes made of iron plates and bound and clamped together in a way that allows the sides to be removed when required; wooden frames are used in the case of mottled soaps.
If it fails to form a hard cake on cooling, a known weight of wax may be added and the product re-heated.
A sublimate may be formed of: sulphur - reddish-brown drops, cooling to a yellow to brown solid, from sulphides or mixtures; iodine - violet vapour, black sublimate, from iodides, iodic acid, or mixtures; mercury and its compounds - metallic mercury forms minute globules, mercuric sulphide is black and becomes red on rubbing, mercuric chloride fuses before subliming, mercurous chloride does not fuse, mercuric iodide gives a yellow sublimate; arsenic and its compounds - metallic arsenic gives a grey mirror, arsenious oxide forms white shining crystals, arsenic sulphides give reddish-yellow sublimates which turn yellow on cooling; antimony oxide fuses and gives a yellow acicular sublimate; lead chloride forms a white sublimate after long and intense heating.
If the substance does not melt but changes colour, we may have present: zinc oxide - from white to yellow, becoming white on cooling; stannic oxide - white to yellowish brown, dirty white on cooling; lead oxide - from white or yellowish-red to brownish-red, yellow on cooling; bismuth oxide - from white or pale yellow to orange-yellow or reddish-brown, pale yellow on cooling; manganese oxide - from white or yellowish white to dark brown, remaining dark brown on cooling (if it changes on cooling to a bright reddishbrown, it indicates cadmium oxide); copper oxide - from bright blue or green to black; ferrous oxide - from greyish-white to black; ferric oxide - from brownish-red to black, brownish-red on cooling; potassium chromate - yellow to dark orange, fusing at a red heat.
If the bead is coloured we may have present: cobalt, blue to violet; copper, green, blue on cooling; in the reducing flame, red when cold; chromium, green, unaltered in the reducing flame; iron, brownish-red, light-yellow or colourless on cooling; in the reducing flame, red while hot, yellow on cooling, greenish when cold; nickel, reddish to brownish-red, yellow to reddish-yellow or colourless on cooling, unaltered in the reducing flame; bismuth, yellowish-brown, light-yellow or colourless on cooling; in the reducing flame, almost colourless, blackish-grey when cold; silver, light yellowish to opal, somewhat opaque when cold; whitish-grey in the reducing flame; manganese, amethyst red, colourless in the reducing flame.
When liquefied it boils at -89.8° C., and by further cooling may be solidified, the solid melting at -102.3° C. (W.
Soc., 18 9 0, 5, p. 59 o), by distilling arsenious oxide with nitric acid and cooling the distillate, obtained a green liquid which consisted of nitrogen trioxide and peroxide in varying proportions, and concluded that the trioxide could not be obtained pure.
It is an orange-coloured gas which may be readily liquefied and by further cooling may be solidified.
Immersed in cold water gelatin does not dissolve but swells up; it dissolves readily in hot water, forming, according to the quantity present, a thick jelly which solidifies to a hard mass on cooling (the " glue " of the woodworker), or a thin jelly (used in cookery).
As cooling progresses the glassy rock contracts and strain phenomena appear in consequence.
To the kettle, two-thirds full of crystals of lead, is now added lead of the same tenor in silver, the whole is liquefied, and the cooling, crystallizing, skimming and ladling are repeated.
It is artificially obtained by adding hydrochloric acid to a solution of lead salt, as a white precipitate, little soluble in cold water, less so in dilute hydrochloric acid, more so in the strong acid, and readily soluble in hot water, from which on cooling, the excess of dissolved salt separates out in silky rhombic needles.
It melts at 485° and solidifies on cooling to a translucent, horn-like mass; an early name for it was plumbum corneum, horn lead.
Since the demagnetizing factor was o 052, the strongest field due to the coil was about 1340; but though arrangements were pro vided for cooling the apparatus by means of o ice, great difficulty was experienced owing to heating.
For ordinary steel the critical temperature, at which magnetization practically disappeared, was found to be about 830°, and the curious fact was revealed that, on cooling, magnetization did not begin to reappear until the temperature had fallen 40° below the critical value.
They found that the permeability of Swedish iron, tungsten-steel and nickel, when the metals were cooled to - 186°, was diminished in weak fields but increased in strong ones, the field in which the effect of cooling changed its sign being 115 for iron and steel and 580 for nickel.
Became definite and cyclic. When the permanent magnetic condition had been thus established, it was found that in the case of all the metals, except the two alloys containing large percentages of nickel, the magnetic moment was temporarily increased by cooling to - 186°.
This solution is allowed to stand for some time (in order that any calcium sulphate and basic ferric sulphate may separate), and is then evaporated until ferrous sulphate crystallizes on cooling; it is then drawn off and evaporated until it attains a specific gravity of 1.40.
Laplace treated the subject from the point of view of the gradual aggregation and cooling of a mass of matter, and demonstrated that the form which such a mass would ultimately assume must be an ellipsoid of revolution whose equator was determined by the primitive plane of maximum areas.
The metal is dimorphous: by cooling molten tin at ordinary air temperature tetragonal crystals are obtained, while by cooling at a temperature just below the melting point rhombic forms are produced, When exposed for a sufficient time to very low temperatures (to - 39° C. for 14 hours), tin becomes so brittle that it falls into a grey powder, termed the grey modification, under a pestle; it indeed sometimes crumbles into powder spontaneously.
It crystallizes (in long needles) more easily when gently agitated during the cooling, or when mixed with such substances as kieselguhr.
In a mine with two shafts a ventilating current may result from other conditions creating a difference in the temperature of the air in either shaft - for example, the cooling effect of dropping water or the heating effect of steam pipes.
They pass through a viscous stage in cooling from a state of fluidity; they develop effects of colour when the glass mixtures are fused with certain metallic oxides; they are, when cold, bad conductors both of electricity and heat, they are easily fractured by a blow or shock and show a conchoidal fracture; they are but slightly affected by ordinary solvents, but are readily attacked by hydrofluoric acid.
A similar glass, if its cooling is greatly retarded, produces throughout its substance minute crystals of metallic copper, and closely resembles the mineral called avanturine.
Cooling the manufactured objects sufficiently slowly to allow the constituent particles to settle into a condition of equilibrium, is of vital importance.
Processes of annealing, or very gradual cooling, are intended to relieve these strains, but such processes are only completely effective when the cooling, particularly through those ranges of temperature where the glass is just losing the last traces of plasticity, is extremely gradual, a rate measured in hours per degree Centigrade being required.
This is generally effected by adding the calculated amount of potassium chloride (of which immense quantities are obtained as a by-product in the Stassfurt salt industry) dissolved in hot water to a saturated boiling solution of sodium nitrate; the common salt, which separates on boiling down the solution, is removed from the hot solution, and on cooling the potassium nitrate crystallizes out and is separated and dried.
It fuses at 339° to a colourless liquid, which solidifies on cooling to a white fibrous mass, known in pharmacy as sal prunelia.
After cooling, the casing is lifted out of the drum by a crane, assisted by compressed air, and is then conveyed by a travelling crane to a vertical centrifugal, inside of which it is made fast.
It melts at 160°, and on cooling solidifies to a glassy mass, which on standing gradually becomes opaque and crystalline.
Hence, supposing the crystals immediately after their formation to be in absolute contact with one another all round, then, in the case of Class II., such contact will be maintained on cooling, while in the case of Class I.
Such sheet or wire then remains flexible after cooling, the originally only loosely cohering crystals having got intertwisted and forced into absolute contact with one another - an explanation supported by the fact that rolled zinc has a somewhat higher specific gravity (7.2) than the original ingot (6.9).
If the cooling is very gradual - occupying several weeks - it sometimes happens that the entire contents of a large crucible, weighing perhaps 1000 lb, are found intact as a single mass of glass, but more frequently the mass is found broken up into a number of fragments of various sizes.
In an American process the glass is drawn direct from the molten mass in the tank in a cylindrical form by means of an iron ring previously immersed in the glass, and is kept in shape by means of special devices for cooling it rapidly as it leaves the molten bath.
It is, however, equally important that the glass as a whole should be flat and remains flat during the process of gradual cooling (annealing), otherwise great thicknesses of glass would have to be ground away at the projecting parts of the sheet.
In the walls and floor of the kiln special cooling channels or air passages are provided and by gradually opening these to atmospheric circulation the cooling is considerably accelerated while a very even distribution of temperature is obtained; by these means even the largest slabs can now be cooled in three or four days and are nevertheless sufficiently well annealed to be free from any serious internal stress.
While he also prevents interruption of the operation by means of water-jackets, he uses hot-blast, and produces, besides metallic lead, large volumes of lead fumes which are drawn off by fans through long cooling tubes, and then forced through suspended bags which filter off the dust, called "blue powder."