PROPORTIONS DETERMINATE. 



189 



209 



210 

 211 

 212 

 213 

 214 

 J 1 5 

 216 

 217 



219 

 220 

 221 

 222 

 223 

 224 

 225 



226 



227 

 228 



Sulphate of ammonia 

 Sulphate of potash 

 Bisulphate of potash 

 Sulphate of soda 

 Hydrous sulphate of lime 

 Anhydrous sulphate of lime 

 Sulphate of barytes 

 Bisulphate of barytes 

 Sulphate of strontian 

 Sulphate of magnesia 

 Sulphate of glucina 

 Bisulphate of glucina 

 Subsesquisulphate of glu- 

 cina 



Sulphate of Alumina 

 Sulphate of iron 

 Persulphate of iron 

 Tripersulphate of iron 

 Sub-bipersulphate of iron 

 Sulphate of nickel 

 Sulphate of cobalt 

 Sulphate of manganese 

 Sulphate of zinc 

 Sulphate of lead 

 Bisulphate of copper 

 Subsulphate of copper 

 Sulphate of bismuth 

 Subsulphate of bismuth 

 Sulphate of mercury 

 Turpeth mineral, or per-") 

 sulphate of mercury J 

 Bipersulphate of mercury 

 Sulphate of silver 

 Sulphate of platinum 



1 s 



1 s 

 1 5 



Is 



lm 

 1 si 

 }pl 



32-000 



37-000 

 19-750 

 28-625 



Since Dr. Thomson regards water as composed of 

 an atom of oxygen and one of hydrogen, it follows 

 that in most substances, the weight he assigns to the 

 atom, is twice the weight of the volume in a gaseous 

 form, compared with the weight of the volume of oxy- 

 gen in a gaseous form. 



Dr. Wollaston, without expressly declaring himself 

 a partisan or an opponent of the corpuscular hypothe- 

 sis, looks upon what others have named atoms, or 

 molecules, as relative weights, in which experience 

 has shown that bodies most readily combine. He 

 calls them chemical equivalents. Oxygen with him, 

 is = l-000j and water is composed of an equivalent of 

 oxygen, and one of hydrogen. Wollaston's numbers 

 differ a little from those of Thomson. The equivalents 

 being to each other in fixed proportions, their mutual 

 combinations may be calculated by the Rule of Three. 

 And upon this principle, Dr. Wollaston has invented 

 a very ingenious instrument to facilitate the calcula- 

 tion. It is well known that Gunter's scale, employed 

 in sliding-rules, is divided in such a manner, that the 

 numbers 1, 2, 3, 4, &c. are arranged upon it so as to 

 have their distances proportional to their logarithms. 

 On a similar sliding-rule, covered with card, Dr. 

 Wollaston marks his numbers on the slider; but upon 

 the two sides, in place of writing the numbers, he 

 writes the names of the substances equivalent to them. 

 Thus, whoever knows how to use the sliding-rule, 

 knows also how to use this instrument. Suppose, 



6 



for example, any one wishes to decompose muriate of 

 soda, and to know how much of the decomposing 

 substances is required. He must draw the slider till 

 100 (or such other number as he may choose) cor* 

 responds to muriate of soda. Now, the name* soda 

 and muriatic acid, correspond to the number of parts 

 of soda and of acid contained in 100 parts of the 

 muriate. Opposite to the name sulphuric acid, etands 

 the number of parts of this substance necessary to be 

 used for decomposing 100 parts of the muriate of 

 soda; and in like manner, the names nitrate of silver, 

 sulphate of ammonia, &c. &c. are found opposite to the 

 numbers indicating how many parts of them are ne- 

 cessary to be used in the same operation. The instru- 

 ment we have just described, is a fine monument of 

 its author's genius. Its utility is great; and Dr. 

 Wollaston has so judiciously chosen the bodies mark- 

 ed on it, that the greater part of those commonly em- 

 ployed in laboratories, are to be found in hta list. 

 Vet the scale admits no great extension; because there 

 is not room for iaany names, of which, moreover, se- 

 veral must correspond to the same numbers ; and as 

 the space gets filled with names, it will become more 

 difficult to find the particular one we are in quest of. 

 Besides, when there happen to be two or more equiva- 

 lents of the same substance in a compound body, un- 

 less the number of them is known before hand, it will 

 be difficult to discover the composition. Suppose we 

 wish to find the composition of the sulphate of red 

 oxide of iron. Taking 100 parts, the weight of its 

 equivalent would be found r= 129"5. The slider i 

 drawn till 100 corresponds to the number of the suL 

 phate ; the name sulphuric acid then corresponds to 

 38-7, but in reality it contains 38-7x1^ = 58; so 

 that, to avoid being misled by the instrument, we 

 ought to know that this salt contains the equivalent 

 and half not only of sulphur, but also of .-ulphuric 

 acid, and of oxygen in the oxide. It is on this ac- 

 count, that Dr. Wollaston has omitted most part of 

 such combinations. For some salts, containing wa- 

 ter of crystallization, he has added to the name 

 of the salt, the number of equivalents of water 

 included in it, so that they are indicated by the instru- 

 ment. 



To profit more extensively by this mode of calcula- 

 tion, M. Berzelius has formed an alphabetical list of 

 all the substances whose composition is known, and 

 annexed to it the formulae expressing the number of 

 atoms contained in each substance, and the number 

 expressing its weight, that of oxygen being supposed 

 = 1 -000. By means of these tables, and a common 

 sliding-rule, such as may be found in the shop of any 

 instrument-milker, all manner of compositions may be 

 calculated. This plan has the advantage over that of 

 Wollaston, in so far as its utility is more general, all 

 known substances being comprehended in it ; but the 

 latter is more agreeable, as it presents all the equiva- 

 lents at a single glance. 



Sir H. Davy, in his paper, " On some of the Com 

 binations of oxy muriatic gas and oxygen," &c. PliiL 

 Trans. 1811, observes, in speaking of Mr. Datum's 

 opinions: " I shall enter no further at present into M:I 

 examination of the opinions, results, * * Inflamma- 

 ble bodies, acids, alkalis, &c. must separate in uniform 

 ratii.-." Sir Humphry appears then, whilst he ad- 

 mits that Dalton's results are deducible from 1 

 pothesis, not to approve of the corpuscular theory in 

 itself, regarding it as too hypothetical. In voiume 



