39 mm newly formed clear ice on a lake in Sweden Congelation ice is ice that forms on the bottom of an established ice cover.
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On the surface of lakes, or other bodies of still freshwater, congelation ice is often called black Ice. This ice has frozen without many air bubbles trapped inside, making it transparent. Its transparency reveals the colour, usually black, of the water beneath it, hence the name. This is in contrast to snow ice, sometimes called slush ice, which is formed when slush (water saturated snow) refreezes.
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Keir worked closely with Priestley to investigate the properties of gases. On 3 May 1787 Keir communicated to the Royal Society some "Experiments on the Congelation of the Vitriolic Acid", and on 1 May 1788 "Remarks on the Principle of Acidity, Decomposition of Water, and Phlogiston". Another paper, on "Fossil Alkali", appeared in 1788 in the "Transactions of the Society of Arts". Keir published the first part of his "Dictionary of Chemistry" in 1789.
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Once a crack occurs within the ice cover and begins to expand to make up a lead, the open water inside the lead is exposed to the cold air temperatures and will freeze. Because wind fetch inside a lead is typically very short, wave action is considerably reduced. Ice growth therefore takes place in a low energy regime environment. Following a stage of frazil ice formation, which sometimes results from seeding by snow crystals, the resulting thin ice skim is followed by the growth of congelation ice.
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Calf suet Suet is the raw, hard fat of beef or mutton found around the loins and kidneys. Suet has a melting point of between 45 °C and 50 °C (113 °F and 122 °F) and congelation between 37 °C and 40 °C (98.6 °F and 104 °F). Its high smoke point makes it ideal for deep frying and pastry production. Tallow-beef suet after rendering The primary use of suet is to make tallow, although it is also used as an ingredient in cooking, especially in traditional puddings, such as British Christmas pudding.
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At the behest of the Royal Society, he made useful observations on magnetic declination at Albany 1775–1776. He performed preliminary experiments on the congelation (freezing point) of mercury in 1775, identifying the problem with previous attempts as being due to the abrupt change of volume of the mercury in the thermometer as it changed state. Apparatus for an improved method was devised and after a series of careful experiments 1779–1782, its freezing point was determined at −39 °F. For this work, highly praised by Cavendish, he was awarded the Royal Society's Copley Medal in 1783, jointly with John Goodricke (for unrelated work).
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With any kind of turbulence in the water, these fragments break up further into random-shaped small crystals which form a suspension of increasing density in the surface water, an ice type called frazil or grease ice. In quiet conditions the frazil crystals soon freeze together to form a continuous thin sheet of young ice; in its early stages, when it is still transparent – that is the ice called nilas. Once nilas has formed, a quite different growth process occurs, in which water freezes on to the bottom of the existing ice sheet, a process called congelation growth. This growth process yields first-year ice.
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