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the salt being the same as that of the water of crystallization rozen into ice.

b. In cane and milk-sugar the carbon ceases to occupy space, the hydrogen and oxygen taking up exactly the space of the corresponding quantity of water frozen into ice.

These results are exhibited in the following table. It is especially remarkable that in the ordinary phosphate and arseniate of soda, the atom of basic water disappears as well as the two atoms of soda.

[blocks in formation]

Carbonate of soda Na 0, C 02 + 10H O 143:4 98.6 10 98.0 | 1:463 | 1.454 Phosphate of soda 2NaO, HO,POʻ+ 24H 0 359:1 235.5 24 235.2 1.527 1.525 Sub-phosphate 3Na O, POS + 24H O 381.6 235.2 24 235.2 1.622 1.622

of soda Arseniate of soda 2NaO, HO, As O' +24HO 402.9 232.0 24 235.2 1.713 1.736 Sub-arseniate of 3Na O, As 0% + 24H O 425.2 235.6 24 235.2 1.808 1.804

soda Cane-sugar C"H"0

171 107.4 11 107.8 1.586 | 1.593 Milk-sugar C + H® 0%

360 234.7 24 235.2 1.531 | 1.534

IV. Another class of salts including all the hydrated magnesian sulphates, sulphate of alumina, borax, pyrophosphate of soda, and the alums, possess a volume made up of that of their bases and of their solid water, their acids ceasing to be recognizable in space.

[graphic]

Table 4.

Atomic weight.

Space occupied
by solid water.

Salis.

Sum of spaces
occupied by base
and water.

Formula.

o Space occupied

by base.

Vol. of salt by

Sp. gr. by exp.

Sulphate of copper Cu 0,S 03 + 6H O 124.66
Sulphate of zinc Zn0,803 + 7H O 143:43
Salphate of magnesia Mg 0, 503 + 7H 0 123.67
Salphate of iron Fe 0,S 03 + 7H0 139.0
Sulphate of nickel Ni O, S 03 + 6H O 13174
Salphale of soda Na 0,S 03 + 10H O 161.48
Sulphate of alumina. Al 03,38 03 + 18H 0 333.7
Biborate of soda .. Na 0,2B 03 + 10H O 191.23
Pyrophosphate of soda 2Na , POS + 10H 0 224:15

49.00
68 6
68.6
68-6
58.8
980
176.4
98.0
98.0

6.12 55:12 54:7 2.261 2.279

74.72 74.2 1.919 1.931

74.72 73.5 1.665 1.683 6:12 74.72 73.58 1.860 1.888 6.12 64.92 64.6 2:029 2.037 12:25 110.25 109 9 1.464 1.469 22:05 198.45 | 199.6 1.681 1.671 12:25 110-25 | 110-5 1.734 1.730 24.50 122.50 122:0 1.829 1.836

Table B.

Salts.

Formula.

Potash alum.. AIS 03,38 03 + KO,S 03 + 24H O 476.38 235.2 22-05 17:15 274.4 274-0 1.736 1731 Ammonia alum Al2O3, 3S 03 +NHO,S 03 +24H 0 455-38 235-2 22:05 23-27 280-52 280-2 1.623 1.62) Chrome alam. Cro03,8S 03 + KO,S 03 + 24H O 503-3 235.2 22.05 17:15 274.4 2731 1.834 1.843 Ammonia iron Fe2 0,38 03 +NHO,S 03 +24H 0 481•03 235-2 22:05 23-27 250-52 280-5 1.714 1.715 alumu

It will be seen from these tables that many salts contain one atom of water of crystallization for every unit-volume in their base. Thus sulphate of alumina possesses 18 atoms of water, and the volume of its base is 18 x 1.225. Sulphate of soda has ten atoms of water, and the volume of its base is 10 X 1.225. Biborate of soda also crystallizes with 10 atoms of water. The magnesian sulphates generally crystallize with 7 atoms of water: of these however 2 atoms are united by a inuch less powerful affinity than the rest, being driven off by a heat of 212°, and even under certain circumstances escaping in dry air at ordinary temperatures. The number of atoms of water essential to the crystallized salt may therefore be estimated at 5, which is the actual number contained in the ordinary crystals of sulphate of copper. The volume of the base of these salts is 5 x 1.225. Now the volume of solid water being 9.8 and the unit-volume of the base 1·225, it follows that the volume of the salt (in which the acid does not appear) must be a multiple of 9.8 + 1.225, that is of 11.025. In the first series of researches by Messrs. Playfair and Joule (Chem. Mem. vol. 11. p. 401) numerous tables are given showing that in many classes of salts-sulphates, chlorides, oxalates, &c. the volume in the solid state is a multiple of 11 or of some number very near it. The explanation of this fact is contained in what has just been stated. I

6. State of Aggregation. A compound is at ordinary temperatures either solid, liquid or gaseous. I. A solid compound may be formed:

1. From two gases. Condensation.--Hydrochloric acid gas forms a solid compound with ammoniacal gas, viz. sal-ammoniac.

2. From a gaseous and a liquid body. Absorption.—Mercury absorbs chlorine and oxygen gases, forming solid compounds.

3. From a gaseous and a solid body. Absorption again.—Iron and other solid metals absorb oxygen gas, and hydrate of soda absorbs carbonic acid gas.

4. From two liquids.—Mercury and bromine.

5. From a liquid and a solid. --Mercury forms solid amalgams with several metals; burnt lime mixed with } its weight of water crumbles to solid hydrate of lime; burnt gypsum mixed with water hardens into the state of gypsum combined with water of crystallization.

6. From two solids, generally by fusion. The combinations of metals with one another or with sulphur. II. A liquid compound may be formed: 1. From two gases.

Condensation.-Hydrogen and oxygen gases combine and form water.

2. From a gas and a liquid. Absorption.—Water absorbs bydrochloric acid gas forming solution of hydrochloric acid.

3. From a gas and a solid. Absorption.—Arsenic, antimony, or tin absorbs chlorine gas, forming a liquid metallic chloride.

4. From two liquids. Mixture in its most confined sense.—Water and alcohol; sulphuret of carbon and chloride of sulphur.

5. From a solid substance and one that is liquid at the ordinary or a somewhat higher temperature. Solution in the wet way.-Salts and water, camphor and spirit of wine, sulphur and fatty matters, lead and mercury.

6. From two solids. Sometimes in the cold, as common salt and ice,

bismuth-amalgam and lead-amalgam; sometimes not below a red heat, as carbon and sulphur.

III. A compound gaseous at the ordinary temperature and pressure of the air arises only:

1. From two permanent gases.-Hydrogen and chlorine.
2. From a permanent gas and a liquid. --Hydrogen gas and bromine.

3. From a permanent gas and a solid.-Hydrogen gas and sulphur; oxygen gas and carbon.

Since no compound which is gaseous at ordinary pressures and temperatures is ever formed by the combination of two liquids or two solids or a solid and a liquid, while on the contrary solid and liquid compounds are formed by the union of two permanent gases, it may be surmised that if any of the hitherto undecomposed bodies are really compound, such will probably be found among the solid and liquid classes.

The less completely the mutual affinity of ponderable bodies is satisfied, or in other words, the less complicated the combinations which they form, the stronger is their attraction for beat and the greater their elasticity; those elements which are gaseous under ordinary circumstances have also on an average the smallest atomic weights.

c. Crystalline Form. The crystalline form of a compound probably bears a definite relation to that of its elements. Such a relation however has not yet been completely traced out, partly because the crystalline forms of many important elements, oxygen for instance, are unknown,-partly because one and the same substance, simple or compound, often assumes one or another crystalline form according to circumstances, i.e. exhibits Dimorphism. (q. v.) The existence of such a relation is however apparent from the facts by which Mitscherlich has established his important theory of Isomorphism. The term Isomorphous in its widest sense applies to those bodies which can replace one another in a compound without producing any alteration in the crystalline form of that compound, except small angular differences. Such bodies

may

be divided into the following groups. A. Substances which are isomorphous both in the separate state and in combination.–Substances possessing the same crystalline form and replacing ore another in combination according to equal numbers of atoms without alteration of crystalline form. Arsenic and antimony crystallize in acute rhombohedrons: As 03 exhibits the same crystalline form as Sb 0s, and many double salts containing As 03 as one base, present, according to Mitscherlich, the same crystalline form as the corresponding salts in which As 0 is replaced by Sb O'.

B. Substances which replace one another in compounds according to equal number of atoms. The crystalline form of such substances in the separate state is either different or else unknown; but they replace one another in combinations according to equal numbers of atoms and without alteration of crystalline form. Titanium crystallizes in cubes, tin in regular six-sided prisms; but both Ti O’ and Sn O’ crystallize in square prisms. The crystalline forms of lime and magnesia are unknown, but Ca 0, CO2 and Mg 0, CO2 crystallize in obtuse rhombohedrons. This group of substances may perhaps be hereafter shown to be identical with the first, when we shall have become acquainted with the crystalline forms of these bodies in the separate state and, possibly have discovered that their difference of form may be referred to Dimorphism.

C. Substances which replace one another in combination according to

unequal numbers of atoms. It sometimes happens that one atom of an element contained in a compound is replaced by two or more atoms of another element, or by two other elements without alteration of crystalline form. Hyperchlorate of potash (K 0, CI 0:) has the same form as hypermanganate of potash (KO, Mn? 0); here l'At. chlorine is replaced by 2 At. manganese. Sal-ammoniac (NH' CI) crystallizes in the same form as chloride of potassium; hence K and N H are isomorpbous. In such cases no such chemical resemblance exists between the interchangeable bodies as in cases A and B: thus manganese bears no resemblance to chlorine, nor does nitrogen to potassium,

The following is a general view of the several groups of simple and compound substances which exhibit the same crystalline form with or without slight differences of angular magnitude. Each group of isomor. phous substances is distinguished by a number: if it contains bodies of different stoichiometrical nature it is further subdivided by means of letters. The same substance, if dimorphous or trimorphous, may be repeated in different groups. Mitscherlich's observations are denoted by Mt.

Regular System. 1. Homohedral. a. C (Diamond) P, K, Ti, Bi, cd, Pb, Fe, Cu, Ag, Au.

b. Co As, Zn S, Pb S, Co S, Ag S, KI, Ya I, K Br, Na Br, N H CI,

K CI, Na CI, LCI, Ag CÍ, K F, Na F, Ca F. c. Cu’ 0, Cu’S, Cu? Cl, Hg' Ag. d. As 0?, Sb 0?, Wöhler. e. Mg 0, Al 0', (Spinell),-Mg 0, Fe 0?, (Pleonast),—Zn 0, Al: 0},

(Gahnite),—ZnO, Fe 0', (Franklinite), -Fe 0, Fe? 0?, (Magnetic

iron ore). Abich. f. Ba 0, N 0,-Sr O, N 0,-PLO, NO', and according to Berzelius,

NO. g. N HCl, Pt C1,-NH CI, Ir CI,-K CI, Pt Cl?,-K CI, Ir CI,

K CI, Os Cl”. Berzelius.
h. N H 0, Alo 0, 4S 0', 24Aq.-N H+ 0, Cro 0, 4S 0, 24Aq.-

NHO, Mn 03, 4S 0', 24AQ.-NH' O, Fe 0", 4S 0, 24A9.-
KO, Al? 0?, 4S O’, 24Aq.--KO, Cr? 0), 4S0', 24Aq.-K 0,
Mn? 0', 4S O', 24Aq.-KO, Fe? O', 4S 0°, 24Aq.- Na O, Al 0',

4S 0', 24A2. Mi.
i. KO, Al 03, 4Si 0°, (Leucite).
k. Na 0, Al 09, 4Si 0°, 2Aq, (Analcime),

2. In pentagonal dodecahedrons : Fe S (Iron pyrites). -Co? As S (Cobalt-glance).

Four-membered or Square Prismatic System. 3. Ca 0, W 0?,-Pb O, W 0,—Pb O, Mo 0?, Levy (Pogg. 8, 513), Pb O, Cr 0? Johnston.

4. Ni O, S 0', 7Aq.-Ni 0, Se 09, 7A9.-Zn 0, Se 0', 7A9. Mt.

5. NHO, 21 O, PO,-N H'O, 2HO, As 0,-KO, 21O, PO',KO, 2H O, As O. Mt.

6. 3Cu 0, 2 Ur? 0°, 3P 0', 24 Aq.-3Ca 0, 2Ur? 09, 3P O', 24Aq. 7. 2N H, Ag O, S 0', -2N H', Ag 0 Se 0',-2N H', Ag 0,Cr 0%.

Mt. 8. a. Cu Fe S (Copper pyrites).-6. Mo’O' (Braunite). Kobell. 9. Ti Oo (Rutile), -Sn 0% (Tinstone).

Pb O,

10. a. Ti 0 (Anatase).

b. K 0, 8Ca 0, 15Si 0’, 16Aq [?] (Apophyllite). Kobell. 11. a. 2Zr 0, Si O’ (Zircon). b. 3Ca 0, 2Al O’, 5Si Ó? [?] (Wernerite). Breithaupt.

Two-and-two-membered or Right Prismatic System. 12. Sulphur.-Iodine. 13. As 0?,-Sb O?. Wöhler. 14. a. Fe S (White iron pyrites).-6. Fe? As S* (Arsenical pyrites). 15. a. Mn20, H O (Manganite).

b. 2Ca 0, Al O', 3Si0, A9 [!] (Prehnite). Kobell. 16. a. Ca 0, CO? (Arragonite), Ba O, CO',-Sr 0, C0,-PbO, CO?

6. KO, N 0%. 17. a. Ba O, SO,Sr O, S 0,-Pb O, SO. Mt. b. N HiO, CI 0", -N HO, Mn? 0", -KO, CI 0",-K 0, Mn? 07.

Mt. 18. a. Na 0, S O?,-Na 0, Se 0?,-Ag 0, S 0?,-Ag 0, Se 03 (fig. 59).

Mt. 6. Ba 0, Mn? 07. Mt. 19. a. KO, S0,-KO, Se 0?,-KO, Cr. O?,-KO, Mn 03 (fig. 76).

Mt. b. NH'O, SO', Aq. Mt. 20. a. MgO, SO, 749,-ZnO, SO', 7Aq,-Ni0, SO', 7Aq,Mg 0, Se 03, 7 Aq,—Zn 0, Se 0, 7Aq (fig. 71, 72, 73). Mt.

b. Sb Sp. Kobell. 21. Na 0, PO”, 4A9,-Na 0, As Oʻ, 4 Aq (fig. 64). Mt. 22. 2Mn0, Si O’ (Chrysolite),—2Mn0, Si O'. Berthier.

23. Na 0, Al? 0?, 3sío', 2Aq (Natrolite),—Ca 0, Al’O’, 3Si 0?, 3Aq (Skolezite).

24. Ba 0, CH'0, 3A7 (Acetate of baryta),-Pb O, C'H 0, 3A (Acetate of lead), (fig. 60). Mt. 25. K’ Fe? Cy",-K® Co? Cys

T'wo-and-one-membered or Oblique Prismatic System. 26. a. Sulphur.

6. KO, 28 09, H 0,-K 0, 2Se 0?, HO. Mt. 27. Fe 0, Ta 0% (Tantalite),-FeO, W 0% (Wolfram). Breithaupt.

28. Ca 0, SO, 2Aq,-Ca 0, Se 09, 2Aq. Mt.-FeO, SO, 2Aq. Graham.

29. FeO, SO, 6A9,-Co O, SO, 6Aq,-MnO, S 03, 6Aq,--C. O, Se 09, 6Aq,-Mixtures of Fe 0, $ 0, with Cu O, S03, or with Zn 0, S 03 ; similarly of Cu O, S 0, with Zno, so, or with Ni O, SO?, or with Mg 0, $ 0°; similarly of MnO, S0%, with Mg0, SO, or with Zn 0, SÖ%, always in combination with 6 At. water (fig. 111). Mt.

30. Mg 0, S0?, 7A9,–2n 0, S 0, 7Aq,—Co O, SO’, 7Aq,—Ni 0, S0°, 7A9,-Mg 0, Se 03, 7A9,-Coo, Se 0%, 7Aq. Mt.

31. Na 0, SO', 10Aq,-Na 0, Se 0}, 10Aq,-Na 0, Cr O', 10Aq (fig. 118, 119). Mt.

32. 2N HO, PO, HO,-2N HO, As 0, H , (fig. 93, 94, 95). Mt. 33. 2Na 0, P О', 25Aq,—2Na 0, As Oo, 25Aq, (fig. 96--100). Mt. 34. a. Na 0, 2B O', 10Aq, (Borax).

b. Ca 0, Mg 0, 2Si 0°; (Augite),-Na 0, 2Fe 0, 4Si 02 [?] (Achmite). Kobell.

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