82 



SALT*. 



are not included, since tin* action <>!' tin- hjdrochln- 

 ric acid acts upon metals ;iml oxides of metals 

 through the agency of the chlorine. The same re- 

 mark holds with the hydriodic and other hydra- 

 cids. The only salts included in this order are in 

 fact compounds of the hydracids with ammonia and 

 phosphuretted hydrogen. In some other salts 

 where hydracids are found, the hydracid acts 

 rather as an electropositive ingredient or base 

 than as an acid, and such salts are therefore placed 

 under a different order. 



Order 3d. Sulphuric salts. This order includes 

 no salt, the electropositive or negative ingredient of 

 which is not a sulphuret. The salts of this order 

 are double sulphurets, such as the hydrosulphurets 

 of potassium, sodium, calcium, &c. 



Order 4th. The haloid salts. This order in- 

 cludes no salt the electropositive or negative in- 

 gredient of which is not haloidal. The salts of 

 this order are double salts, and one or other of the 

 ingredients must be analogous to sea salt, such as 

 the hydrogochlorides, aurochlorides, oxychlorides, 

 double iodides, silica fluorides, &c. 



As almost every acid unites with every base, and 

 sometimes in several proportions, it follows that 

 the number of salts must be immense. Several 

 thousands are already known, although not above 

 thirty were believed to exist fifty years ago. The 

 early names of the salts, so far as these bodies were 

 known to chemists, were wholly destitute of scienti- 

 fic precision. At present, however, they are univer- 

 sally designated according to the nomenclature of 

 Morveau. The name of each salt consists mainly 

 of two words, one generic, the other specific. The 

 generic word precedes the specific, and is derived 

 from the acid; the specific comes from the base. 

 For example, a salt consisting of sulphuric acid and 

 soda, is spoken of generically under the name of a 

 sulphate, and specifically, by adding the name of 

 the base; thus sulphate of potash. The termina- 

 tion ate corresponds with the acid whose termina- 

 tion is in ic, and the termination ite with the acid 

 whose termination is in ous; thus sulphuric acid 

 gives sulphates; sulphurous acid, sulphites. There 

 are some acids containing less oxygen than those 

 that terminate in ous : in such case, the word hypo 

 is prefixed; thus we have A/ypo-sulphurous acid, 

 hypo-nitrous acid, giving also salts that are called 

 %/>o-sulphites, and At/po-nitrites. When the salt 

 is a compound of one atom, or proportional of acid 

 with one of base, it is distinguished simply by the 

 words denoting the acid and the base, without the 

 addition of any prefix. If the salt contains two 

 atoms of acid united to one atom of base, the 

 Latin numeral adverb bis or bi is prefixed. Thus 

 bisulphate of potash is a salt composed of two atoms 

 sulphuric acid and one atom potash. Were there 

 three, four, &c., atoms acid, the numeral adverbs 

 ter, quater, &c., would be prefixed. Thus quater- 

 oxalate of potash means a compound of four atoms 

 oxalic acid and one atom of potash. When two 

 atoms of base are combined with one atom of acid, 

 this is denoted by prefixing the Greek numeral ad- 

 verb dis. Thus diphosphate of potash means a 

 compound of two atoms potash with one atom 

 phosphoric acid. The prefixes tris, tetrakis, &c., 

 indicate three, four, &c., atoms of base with one 

 atom of acid. Salts of this description were 

 formerly termed sub-salts; at least in those instances 

 where an alkaline reaction was produced upon test- 

 liquors from the excess of base. 



We have stated above that salts are at present 



understood to lie compound* only of acids and 

 kise-. The discoveries of Sir II. Davy, however, 

 require us to modify this generally received defini- 

 tion. Many bodies, such as common salt and mu- 

 riate of lime, to which the appellation of salt can- 

 not be refused, have not been proved to contain 

 either acid or alkaline matter, but must, according 

 to the strict logic of chemistry, be regarded as 

 compounds of chlorine with metals. Such com- 

 pounds, possessing, for the most part, the proper- 

 ties of solubility in water, and sapidity, are to be 

 included under the general name of salts. They 

 are denominated chlorides, iodides, and bromides, of 

 the metals, according to the particular constitution 

 of each. Thus the compound of chlorine and cal- 

 cium, formerly known as muriate of lime, is called 

 the chloride of calcium. The solubility of salts in 

 water is their most important general quality. In 

 this menstruum they are generally crystallized; 

 and by its agency they arc purified and separated 

 from one another, in the inverse order of their 

 solubility. The determination of the quantity of 

 salt which water can dissolve, is not a very diffi- 

 cult process. It consists in saturating the water 

 exactly with the salt, whose solubility we wish to 

 know, at a determinate temperature, weighing out 

 a certain quantity of that solution, evaporating it, 

 and weighing the saline residue. We shall give 

 the results of some experiments upon the solubility 

 of a few salts. 



Sulphate of Sodn. 



Salt soluble in 100 parts of water. 

 Temperature. Anhydrous. Crystallized. 



0,00 5,02 12,17 



11,67 10,12 20,38 



17,91 16,73 48,28 



28,76 37,35 161,53 



30,75 43,05 215,77 



32,73 50,65 322,12 



40.15 48,78 291 44 



50,40 46,82 262,35 



59,79 45,42 



70,61 44,35 



84,42 42,96 



103,17 42,65 



Hence it appears that the solubility of sulphate of 

 soda follows a very singular law. After having 

 increased rapidly to about the temperature of 33, 

 where it is at its maximum, it diminishes to 103, 17 Q ; 

 and at that point it is nearly the same as- at 30,5. 

 Solubility of Chloride of Potassium. 



Salt dissolved 

 in 100 water. 



43,50 



55,63 



65,51 



77,89 



Temperature. 



15,64 

 49,31 

 74,89 

 105,48 



Solubility of Chloride of Sodium (common salt). 



Salt dissolved 

 Temperature. in , 00 water 



13,89" 35,81 



1690 35,88 



59,93 37,14 



109,73 40,38 



Solubility of Sulphate of Magnesia (Epsom salt). 



Salt dissolved 

 Temperature. m 100 water . 



14,58* 103.69 



39,86 178,34 



49,08 212,61 



64,35 295,13 



97,03 644,44 



Solubility of Nitrate of Potash (Nitre;. 



Temperature. 



0,00 



5,01 

 11,67 

 17,91 

 24,94 



5,13 



Salt dissolved 

 in 100 water. 



13.32 



16.72 



2223 



29,31 



38,40 



54,83 



Temperature. 



48,10 



f>472 

 65,45 

 79,72 

 97,66 



Salt dissolved 

 in 100 water. 

 74,66 

 97,05 

 125,42 

 169.27 

 236,4* 



