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extracted with a mixture of alcohol and acetic acid in order to remove carbonate of potash, the double sulphate of potash and soda remains in the crystalline state, and therefore emits no light when dissolvedana crystallized.) Chloride of potassium fused with sulphate of soda likewise exhibits the luminous appearance. A bright light is also emitted by neutral chromate of potash fused with sulpbate of soda, whereby crystals are formed, consisting mainly of the double sulphate of potash aud soda with only 3 per cent. of chromic acid : moreover, by 2 parts of bichromate of potash fused with 1 part of dry carbonate of soda, -in which case crystals are produced having the form of sulphate of potash and containing 3 atoms of chromate of potash combined with 1 atom of chromate of soda; and finally by a mixture of 1 atom of seleniate of potash with 1 atom of sulphate of soda, which produces crystals having also the form of sulphate of potash, and containing only 5 per cent. of selenic acid, together with potash, soda, and sulphuric acid. (H. Rose.)

A saturated solution of fluoride of sodium very slowly evaporated emitted a great number of bright sparks of a pale yellow colour, which proceeded sometimes from one sometimes from another part of the crystals as they formed, increased when the liquid was disturbed, and did not cease till it was completely evaporated. On repeating the experiment with the same salt and the same vessel, nothing further was seen (Berzelius).—Likewise observed by H. Rose. (Pogg. 52, 589.).

A solution of nitrate of strontia, which had been for a long time exposed to air and light, emitted many sparks when evaporated and crystallized in a stoneware vessel; these sparks showed themselves particularly when the crystals were touched with a glass rod or metallic wire, and also when the vessel was shaken. On redissolving and recrystallizing the salt, this appearance was not reproduced, though the mode of experimenting was varied in every possible way. (Pfaff.) Likewise observed by Stieben. (Pharm. Central Bl. 1836, 400.)

A solution of 8 parts of acetate of potash evaporated till it ceased to swell

up,

and fell to pieces, shone brightly, when left over the fire, as if it were red hot. (Büchner.) (Slow combustion ?)

On subliming benzoic acid with ; of its weight of charcoal powder on a plate covered with a glass receiver and strongly heated, Büchner observed numberless sparks moving up and down as long as the sublimation continued.

Addendum to the remarks on the incandescence of bodies (p. 107): A body does not always increase in density by incandescence. Uranotantalite, which exhibits vivid incandescence, has a sp. gr. of 5.517 before incandescence and 5.485 after.-- Incandescence takes place without perceptible development of heat: at all events, no rise of temperature can be perceived in the case of oxide of chromium, in which the incandescence is very bright. (The development of light observed in the crystallization of arsenious acid from its solution in hydrochloric acid is likewise unattended with disengagement of heat.) Whilst according to this, many bodies in passing from the amorphous to the crystalline state merely develop light, others on the contrary develop heat, e. g. grape-sugar (p. 106). H. Rose, Pogg. 52, 589.)

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Boerhaave, Elementa Chemiæ. 1, 126-424.
Bergman, de Materia Caloris. Opusc. 3, 418.
Scheele. Properties of Heat; in his Abhandl. von Luft und Feuer, 53.
Wilke, on Specific Heat. N. Abhandl. d. Schwed. Akad. d. Wiss. 1782,

2, 489. Gadolin, on Specific Heat. Crell. Ann. 1786, 1, 263 and 340. Lavoisier & Laplace. Mém. de l'Acad. d. Sc. 1780, 355; also Crell. Ann.

1787, 1, 263, 344 and 546; 2, 62.-Again : Schw. 25, 355. Guyton-Morveau. Pyromètre. Ann. Chim. 90, 113 and 224. Mayer. C'eber die Gesetze und Modificationen des Wärmestoffs. Erlangen,

1791. On the Specific Heat of various kinds of Wood. Crell. Ann.

1798, 1 and 443. Crawford. Experiments and Observations on Animal Heat. Leipz. 1789. Pictet. Essais Physiques sur le Feu. Gen. 1790. Leslie. Enquiry into the Nature of Heat. 1804. Böckmann. Versuche über die Wärmeleitung verschiedener Körper. Karls

ruh, 1812. Rumford. Gren. N. J. 4, 418.-Gilb. 1, 204, 323 and 436; 2, 249; 3,

309; 4, 85, 222 and 330; 5, 206 and 288; 9, 61; 12, 553; 13, 385;

17, 33 and 213; 20, 177 and 369; 44, 1; 45, 1, 142 and 306. Dalton. New System of the Chemical Part of Natural Philosophy.

Manchester, 1808, 1, 1. Delaroche. Radiant Heat. J. Phys. 75, 201. Delaroche & Bérard. Specific Heat of Gases. Ann. Chim. 85, 72 and

113. Clement & Desormes. Freezing by Evaporation. Ann. Chim. 78, 183;

also Gilb. 43, 378.—Absolute Zero and Specific Heat. J. Phys. 89,

321 and 428. Despretz. Cooling of Metals in the Open Air. Ann. Chim. Phys. 6,

184 —Spec. Gr. of Vapours. Ann. Chim. Phys. 21, 143.—Latent Heat of Vapours. Ann. Chim. Phys. 24, 323. Shifting of the Zero in Thermometers. Ann. Chim. Phys. 64, 312,—Conducting Power of Solids for Heat. Ann. Chim. Phys. 36, 422: also Pogg. 12, 281.- Development of Heat in Combustion. Ann. Chim. Phys. 26, 343; 37, 180 and 182; also Pogg. 12, 519 and 520.-Freezing. Compt. rend. 2, 19; also Pogg. 41, 492.—Conducting Power of Water. Ann. Chim. Phys. 71, 206; also Pogg. 46, 340.—Maximum Density of Saline Solutions. Ann. Chim. Phys. 70, 45 and 73, 296. Heat of

Fluidity. Compt. rend. 11, 806; abstr. Pogg. 52, 177. Gay-Lussac. Expansion of Gases by Heat. Ann. Chim. 43, 137; abstr.

Gilb. 12, 256.-Specific Gravity of Vapours. Ann. Chim. 80, 218; also Gilb. 45, 332.—Specific Heat of Gases. Ann. Chim. 81, 98; also Gilb. 45, 321.—Expansion of Liquids by Heat. Ann. Chim. Phys. 2, 130.– Evaporation in vacuo. Mém. d'Arcueil, ], 204 ; also N. Gehl. 5, 655; also Gilb. 27, 147.-Production of Cold by the Expansion of Gases. Ann. Chim. Phys. ?, 305.—Heat in the vacuum.

Ann. Chim. Phys. 13, 303.-Production of Cold during VOL. I.

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evaporation in the Open Air. Ann. Chim. Phys. 21, 82; abstr. Schw. 36, 411.-Boiling Point of a Mixture of Two Liquids. Ann. Chim.

Phys. 49, 393 (also Pogg. 25, 498); 50, 111. Dulong & Petit. Laws of Cooling. Ann. Chim. Phys. 7, 225 and 337;

also Schw. 25, 325 and 343 - Specific Heat. Ann. Chim. Phys. 10,

395; also J. Phys. 89, 81 and 428; abstr. Schw. 28, 121. Dulong. Specific Heat of Gases. Ann. Chim. Phys. 41, 113; also Pogg.

16, 435.-Development of Heat in Combustions. Compt. rend. 7,

871; also Pogg. 45, 461; also J. pr. Chem. 16, 438. Poisson. Ann. Chim. Phys. 19, 337; 23, 337 (also Gilb. 76, 269); 26,

225; 27, 236. Fourier. Ann. Chim. Phys. 4, 128; 6, 259; 27, 236 (also Pogg. 2, 358);

28, 237.-Conduction of Heat. Ann. Chim. Phys. 37, 291; abstr.

Pogg. 13, 327. Herapath. Ann. Phil. 17, 273, 340 and 401; 18, 50, 89, 201, 256, 303,

363, 434 and 462; 19, 16, 29, 290; 23, 349. Comp. also Ann. Phil.

18, 223; 390 and 418. Ure. Phil. Transact. 1818, 2, 329; also Schw. 28, 329. Dulong & Petit. Expansion by Heat. Ann. Chim. Phys. 2, 240; also

Gilb. 58, 254.—Measurement of Temperature. Ann. Chim. Phys. 7,

113; also J. Phys. 86, 113; also Schw. 25, 30-4. Navier, sur la Variation de Température qui accompagne les Changemens

de Volume des Gas. Ann. Chim. Phys. 17, 373. Haykraft. Specific Heat of Gases. Transact. of the R. Soc. of Edinb.

10, 195; also Gilb. 76, 289. Leslie. Cold by Evaporation. Gilb. 43, 473; again: Schw. 20, 467. Configliachi. Čold by Evaporation. Gilb. 43, 341. Muncke, on the Elasticity and Density of Vapours. Schw. 22, 1; more

fully in his Physikal. Abhandl. Giessen, 1816. Cagniard de la Tour. Formation of Vapour. Ann. Chim. Phys. 21,

127 and 178; 22, 410. Forbes. Polarization of Heat. Phil. Mag. J. 6, 134, 205, 284 and 366.

Transact. of the Roy. Soc. of Ed. vol. 14; abstr. Pogg. 45, 64. Prevost. Ann. Chim. Phys. 31, 429; 38, 41; 39, 194 (the last also in

Pogg. 14, 595). Baden Powell

. Ed. J. of Sc. 3, 297; also Pogg. 21, 311.-N. Ed. J. of Sc. 2, 297.Phil. Trans. 1834, 485; also Pogg. 34, 636. Faraday. Limits of Evaporation. Ann. Chim. Phys. 28, 436; also

Pogg. 9, 1.-J. Ray. Inst. 1, 70.–Liquefaction and Solidification of

Gases. Phil. Trans. 1845, 170; abstr. Phil. Mag. J. 26, 253. Apjohn. Specific Heat of Gases. Phil. Mag. J. 13, 261 and 339. Potter. Specific Heat. N. Ed. J. of Sc. 5, 575; 6, 166. Neumann. Specific Heat. Pogg. 23, 1. Magnus. Boiling Points of Mixtures and Compounds of two Liquids.

Pogg. 38, 481.—Expansion of Gases. Pogg. 55, 1; 57,177. Tension

of Aqueous Vapour. Pogg. 61, 225. Hermann. Specific Heat. Nouv. Mém. de la Soc. de Mosc. 3, 137. Radberg. Melting Points of Metallic Alloys. Pogg. 18, 240.—Specific

Heat of Salts. 35, 474.-Expansion of Gases by Heat. Pogg. 41,

271; 44, 119. Avogadro. Specific Heat. Brugn. Giorn. 19, 16.-Ann. Chim. Phys.

55, 80; 57, 113. Suermann. Specific Heat of Gases. Ann. Chim. Phys. 63, 315; also

Pogg. 41, 474.

Regnault. Specific Heat. Ann. Chim. Phys. 73, 5; 76, 129; also Pogg.

51, 44 and 213; 53, 60 and 243; 62, 50.-Latent Heat of Water.
Pogg. 62, 42.--Elasticity of Gases. Pogg. 67, 354 - Expansion of
Gases by Heat. N. Ann. Chim. Phys. 4, 5; 5, 52.-Comparison of
the Mercurial and Air Thermometers. N. Ann. Chim. Phys. 5, 83;
6, 370.–Tension of Aqueous Vapour. N. Ann. Chim. Phys. 11,
334; 13, 196.
Relation des Expériences entreprises ....

· pour déterminer les Principales Lois et les données numériques qui entrent dans le Calcul des Machines à Vapeur. Paris, 1847.-[A translation of part of this work, relating to the Latent Heat of Steam at Different Pressures, is

given in Vol. I of the “Works of the Cavendish Society."] De la Rive & Decandolle. Conduction of Heat by various kinds of

Wood. Mém. de la Soc .de Genève, 4, 70. De La Rive & Marcet. Specific Heat of Solids. Ann. Chim. Phys. 75,

113; 77, 121.-Specific Heat of Gases. Ann. Chim. Phys. 33, 209; 35, 5; also Pogg. 10, 363; also N. Tr. 17, 1, 217;—Bibl. univ. 41, 37; also Pogg. 16, 340; also Schw. 55, 417;—Ann. Chim. Phys. 41,

78. Melloni. Pogg. 24, 640; 35, 112, 272, 385 and 529; 37, 212, 218, 486

and 494; 38, 1 and 203; 39, 250, 456 and 544; 43, 18 and 257; 44,

124; 45, 1; 51, 73; 52, 421; 53, 47; 62, 30. Walker, on the Production of Artificial Cold. Gren. N. J. 1, 420;

Gren. N. J. 3, 458. Fourcroy & Vauquelin; Rouppe; Guyton-Morveau; Van Mons; Hassen

fratz and others. Experiments on Artificial Cold. Scher. J. 3, 49. Pouillet, on the Development of Heat by application of Moisture. Ann.

Chim. Phys. 20, 141; also Gilb. 73, 356; abstr. Schw. 36, 193.

Solar Heat and Temperature of Space. Pogg. 45, 25.
Pambour. Quantity of Heat and Tension of Vapour of Water. Institut.

Nr. 256; abstr. Jahresbericht, 19, 52;—Compt. rend. 6, 373; abstr.
Jahresbericht, 19, 56;--Compt. rend. 12, 655; also Pogg. 53, 234.-

Further, Pogg. 59, 187.
Hess. Development of Heat accompanying Chemical Combination.

Pogg. 47, 210; 50, 385; 52, 97 and 114; 53, 499 and 535. De la Prevostaye & Desains. Experiments on the Latent Heat of Water.

Pogg. 59, 163; 61, 30.-Radiant Heat. N. Ann. Chim. Phys. 16,

337; also Pogg. 64, 5; 67, 2335; 69, 367. Schröder. Relation between the Boiling Points and Composition of

Chemical Compounds. Pogg. 62, 184 and 337; 64, 96 and 367;

67, 45. Pleischl. Description of a New Thermometer or Cryometer. Pogg. 63,

115. Langberg. Conducting Power of Solids. Pogg. 66, 1. Andrews. Change of Temperature accompanying Basic Substitutious.

Phil. Trans. 1814, I, 21; abstr. Phil. Mag. J. 24, 457.—Development of Heat in the Combination of Bodies with Oxygen and Chlorine. Phil. Mag. J. 32, 321 and 426.-Latent Heat of Vapours.

Qu. J. of Chem. Soc. 1, 27. Münke. Tension of Vapour of Water at Low Temperatures. Pogg. 67,

376. Pierre. Dilatation of Liquids. N. Ann. Chim. Phys. 15, 325; 19, 193;

20, 5; 21, 336.

H. Kopp. Boiling Points and Expansion of Liquids. Pogg. 72, 1 and

223; abstr. Ann. Chem. Pharm. 64, 212. Playfair & Joule. Maximum Density of Water. Memoirs of Chem. Soc.

2, 199.—Expansion of Solids. Qu. J. of Chem. Soc. 1, 121. Person. Latent Heat of Liquids. N. Ann. Chim. Phys. 21, 295; also

Pogg. 70, 300; abstr. Ann. Chem. Pharm. 74, 179.-Shifting of the

Zero in Thermometers. Pogg. 65, 370. Knoblauch. Radiant Heat. Pogg. 70, 205 and 337; 71, 1; abstr. Ann.

Chem. Pharm. 74, 193. Senarmont. Conducting Power of Crystallized Bodies. N. Ann. Chem.

Phys. 24, 457. Favre & Silbermann. Specific Heat of Liquids and Latent Heat of

their Vapours. Comptes Rendus. 23, 524.-Development of Heat in

Combustion. Ann. Chem. Pharm. 60, 165, Grassi. Development of Heat in Combustion. Journ. de Pharm. 8,

170; abstr. Ann. Chem. Pharm. 56, 185. Grove. Decomposition of Water by Heat. Phil. Mag. J. 30, 58; 31, 96. Graham. Development of Heat in the combination of Acids and Bases.

Phil. Mag. J. 22, 351; 24, 401.

SYNONYMES. Caloric, Chaleur, Wärmestoff, Wärmematerie. Heat or Caloric is that substance whose entrance into our bodies is supposed to occasion the sensation of warmth or heat, and its egress the sensation of cold.

Physical Properties. 1. It is invisible.

2. Without weight.--Oil of vitriol and water have the same weight before mixture and cooling as afterwards. The weighing of cold and heated balls in the air proves nothing.

3. It is very elastic, and shows great tendency to expand. -Two easily moveable bodies, heated in vacuo, repel one another,-a proof that heat is in its own nature repulsive. (Fresnel, Ann. Chim. Phys. 29, 57, and 107; also Pogg. 4, 355.)—The coloured rings formed between a lens and a flat plate of glass vary in tint when heated, in such a manner as to show an increase of distance between the lens and plate. (Baden Powell.)— The fine soft powder of silica separated hy acids from solutions of that substance, or magnesia in a similar condition heated to redness in a platinum dish over a spirit lamp, appears to swim in the dish, becomes very mobile, and places itself horizontally when the dish is turned on one side-an effect which proceeds from the repulsive force of heat (or from the escape of heated air.* Gm.?) (Addams, Phil. Mag. J. 18, 415.)

4. Through a vacuum, through elastic fluids, and through many liquid and solid bodies, it spreads itself out from its origin in straight lines, as Radiant Ileat, with a great and hitherto unmeasured velocity. Its in

* This semifluid state of a pulverulent substance is well seen when bicarbonate of soda is heated in a large crucible for the purpose of converting it into carbonate; also in the conversion of oxalate of cerium into the peroxide of that metal by ignition. In these cases the effect is evidently due to the escape of heated gases: the fine particles of the powder float in the atmosphere formed around them by the gases before they finally escape. [W.]

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