EQUIVALENTS. J 



CHEMISTRY. 



Btitution of the compound is shown : thus, sulphate of 

 iron is represented as Fe O + SOj + 7HO ; that is, it is 

 composed of one equivalent of oxide of iron, one of 

 sulphuric acid, and seven of water. 



In many chemical works, the sign 4- is omitted, and 

 the symbols are written thus Cu O, SOa, 5HO, which is 

 that of the sulphate of copper, or "blue vitriol." This, 

 of course, saves space, and is equally as intelligible as 

 the method above named. 



We may now show how these symbols are employed 

 in connection with the actual value of the separate 

 equivalents of a compound ; and we would advise the 

 student to commit to memory the different values as- 

 signed thereto. He will thus readily become acquainted 

 with that of any compound. A table of these equivalents 

 will be found prefixed to the next chapter. The following 

 skeleton table will serve the purposes of illustration. In 

 it we have used whole numbers, so as to save any 

 difficulty with fractional parts. 



Skeleton Table of Equivalents and Symbols. 

 Nan.. Symbol. Equivalent. 



1 



8 



6 



14 



16 



20 



36 



23 



108 



Hydrogen ...... H 



Oxygen ....... O 



Carbon ....... C ..... 



Nitrogen ...... N 



Sulphur ...... S 



Calcium ...... Ca 



Chlorine ...... Cl 



Sodium ....... -Na (Natrium) 



r ....... Ag (Argentum) 



In the above we have included the elements only ; but 

 in the next table, we have the equivalents of bodies 

 which are composed of some of these elements. 



Skeleton Table of the Symbols and Equivalents of tome 

 Compounds. 



Name. Symbol. 



Water ....... HO 



Sulphuric acid (dry) . . SO. 

 Sulphuric acid, with one"! 



equivalent of water, as > SOj 



found iu commerce . J 



Carbonic acid .... COj 



Cartnate'ofiime ] | } Ca O, CO. 



Common salt . 1 XT ra 



Chloride of sodium . . / Na > C[ 



Chloride of silver ... Ag, Cl . 



It will thus be seen that the symbols and equivalents 

 of a compound are composed of those of their elementary 

 constituents. 



We may now proceed to illustrate the method adopted 

 for showing the results obtained in adding compounds 

 in solution together, by which decomposition and the 

 production of new compounds are effected. 



Decomposition of Nitrate of Silver by means of Common Salt. 



HO 



Equivalent. 



9 

 40 



. 49 



22 

 . 60 



e/> 



69 



. 144 



We have already done this to some extent in a previous 

 page;* but did not there include the equivalents and 

 symbols of the substances mentioned. In the preceding 

 example, in which the decomposition of nitrate of silver is 

 exhibited, each point is illustrated : and we recommend 

 the student to study them carefully, so that he may have 

 no difficulty in following our remarks in future pages. 

 We have introduced the name of the materials employed, 

 their symbols and equivalents, and those of the re- 

 sulting compounds. 



From the diagram, illustrating the decomposition of 

 nitrate of silver by common salt, we find that 36 parts 

 of chlorine leave the salt, and combine with 108 parts 

 of silver, forming 144 parts of chloride of silver. Also 

 that 54 parts of nitric acid, and one of oxygen, leave the 

 silver in the nitrate, to combine with 23 parts of sodium, 

 and so form 85 parts of dry nitrate of soda. We thus 

 learn, that whilst the total amount of parts employed and 

 obtained are equal viz., 229 grains, ounces, or pounds 

 yet that the materials used, and the products of their 

 mixture, are entirely different in every respect. 



There are some theoretical considerations which might 

 be noticed in reference to the formation of salts, by the 

 addition of an acid to the oxide of a metal. Some 

 would transfer the oxygen of the oxide to the acid. 

 Thus, instead of indicating sulphate of copper, as 

 Cu, O -f- SOj -j- 5HO; it would, according to such views, 

 be Cu -f- SO 4 -f- 5HO. On this point, however, we 

 shall have to remark hereafter. Dr. Daniell, of King's 

 College, London, the Inventor of the voltaic battery 

 bearing his name, was, we believe, the first to broach the 

 doctrine. 



SPECIFIC GRAVITY, ISOMORPHISM, DIMOR- 

 PHISM, ISOMERISM, ETC. 



Materials used. 



Name. Symbol. Equivalent. 



Nitrate of | . n vn 

 Silver, j AgO, SO j 



Composed of 



Silver 1 Ag i08 



Oxygen ...j 8 



Nitric Acid. 



Nitrogen... \ N II 



SofOxygen) O. 40 



170 

 To which is added 



Chloride of) _. 

 Sodium. ( Na ' C1 



Composed of 

 Sodium ... \ Na 23 



Cllonne...| 01 36 



Totai 229 



Name. 



WE shall now refer to some matters connected with the 

 physics of chemistry, in which the relative weight and 

 forms of bodies are involved. We shall first explain how 

 the specific gravities of solids, liquids, and gases are 

 obtained ; and then refer to some physical peculiarities 

 noticed in crystalline and other bodies. 



By the term "specific gravity," we mean that the 

 Bailie bulk of different bodies weighs differently ; or, 

 in other words, some substances contain, within any 

 specific limit, more matter than others. For instance, 

 if we fill a bottle of any size with mercury, and 

 weigh it, and then pour away the metal and fill the 

 bottle with water, we shall find, on reweighing it, that 

 only one-fourteenth of the weight of the mercury 

 is required to balance the water. In other words, 

 mercury weighs, bulk for bulk, fourteen times nearly 

 that of water. Almost every substance we meet with 

 has thus a weight of its own, and this weight is called 

 its specific gravity. With respect to solids, the difference 

 is characteristic in all cases. 



Now there is no difficulty in com- 

 paring the weights of equal bulks 

 Producu. f water and mercury, because, as 



Symbol. Equivalent. eacn i g a liquid, it is easy to weigh 

 equal bulks one against another; 

 but this would be impossible if we 

 were to attempt to ascertain the 

 Nao, xo 65 specific gravity of gold, iron, <tc., 



in a similar manner ; because, to 

 render them fluid, we should have 

 to employ so intense a heat aa 

 would instantly destroy our appa- 

 ratus. This difficulty is easily over- 

 come, in a manner we shall proceed 

 to explain. 



It is scarcelynecessary to remark, 

 that some standard of comparison 

 is required, by means of which a 

 uniform table of specific gravities 

 may be constructed ; and, by uni- 

 Ag, a j44 versa! consent, water at a tempera- 

 ture of 00 Fah., in as pure a state 



Total 229 See antr, p. SOI. 



