Reid's " Elements of Practical Chemistry." 451 



of the common sulphuric acid (96) consist of two equivalents of 

 water (18), and two of dry sulphuric acid (80); the nitrate of pot- 

 ash on the other hand, is composed of one equivalent of potash 

 (48), and one of nitric acid (54). The dry sulphuric acid com- 

 bines with the potash, forming bisulphate of potash, and the water 

 goes to the nitric acid, forming the liquid which is condensed in the 

 receiver :" and we are afterwards informed (p. 56) that the nitric 

 acid of the nitre requires two equivalent portions of water to con- 

 dense it. When we first noticed that according to the above state- 

 ment, 18 added to 80, are equal to only 96, we considered it as an 

 error of the press; but in the following page the same blunder 

 is more conspicuously repeated in a diagram ; we must, therefore, 

 charge Mr. Reid with an extreme want of attention. When cor- 

 rected we admit that this is the view of the subject taken by the 

 late Dr.Wollaston ; but it is not an accurate one, as Mr. Reid might 

 have seen in the second volume of the Phil. Mag. and Annals of 

 Philosophy, p. 430. It is not the dry sulphuric acid only which com- 

 bines with the potash, the bisulphate always contains water, which is 

 essential to its exstence ; consequently the whole of the water does 

 not go to the nitric acid, and two equivalents of water are not re- 

 quired to condense one equivalent of nitric acid. 



Indeed Mr. Reid has given two tables of the strength of liquid 

 nitric acid of different densities ; and if he had examined them, 

 one of two things must have occurred to him : viz. either that his 

 assertion, as to the smallest quantity of water which is capable of 

 condensing a given proportion of nitric acid, was erroneous ; or that 

 these tables were both extremely inaccurate. The first of them is 

 Dr. Thomson's ; it shows not only the per-centage of real acid, but 

 also the atomic constitution; and it surely ought to have excited 

 Mr. Reid's notice, that according to this table it is acid of sp. gr. 

 T4855, which contains 75 per cent of real acid, and which is stated 

 to be constituted of 1 atom of acid, and 2 atoms of water; whereas 

 Mr. Reid asserts that this is the composition and atomic constitu- 

 tion of acid of sp. gr. 15. The second table is Dr. Ure's ; and if he 

 had doubted the accuracy of Dr. Thomson's statement, he would 

 have found its correctness confirmed by referring to Dr. Ure, who 

 mentions that acid of sp. gr. 1-485 contains 74918 per centof real 

 acid. 



It is quite evident that Mr. Reid never compared these things, 

 or he would not have considered that statements so contradictory, 

 as that a table founded on the assumption that acid of P4S55 con- 

 tains 75 per cent of acid, would " be found vei*y convenient to refer 

 to in making experiments," when he had previously asserted that 

 acid of sp. gr. 1500 was of that strength. 



After having mentioned the weights of nitre and sulphuric acid 

 proper to be employed, and adverted to the circumstances attend- 

 ing the use of one atom each of the acid and salt, we did not ex- 

 pect that our author would have given further instructions on the 

 subject ; but to our surprise the following directions occur at p. 56 : 

 " in conducting this process on the small scale, three ounces (water) 



3 M 2 measure 



