Thomson's Sj/slem of Chemistn/. 153 



But in the same page he says, " it follows from the experiments 

 of Davy, that a saturated solution of ammonia is composed of 

 74.63 water + 25.37 ammonia*." But the Doctor's water of 

 0.90Q, which he presently shews was far under saturation, must 

 have contained, by his own statement, S5.74 per cent, ofammo- 

 r'^"i ^'^i '^^"^^"^ '^'^'1 t'"^ absurdity, he plunges into another. 

 1 he following table, for which we are indebted to Mr. Dalton. 

 exhibits the quantity of ammonia contained in ammoniacal solu- 

 tions of different specific gravities. We there observe the fol- 

 lowing numbers : 



.'^pocific gravity of liquid. Arnmoni;! per cent, by weight 



0-85 35.3 



0.87 29.9 



0.90 22.2" 



Now we ask Dr. Thomson, how does 22.2 tally with 35 74 the 

 quantity deduced from his " trials, " at the very same specific 

 gravity, 0.90 ? But what right had he to take up a very old 

 estimate of Sir H. Davy's, and neglect the table given by this 

 philosopher, in his Elements pubhshed in 1812^ Was it that 

 he rnight shew by the comparison of Mr. Dalton's table, that 

 Mr H. Davy was egregiously wrong, in speaking of a saturated 

 solution, with 25.37 ammonia, when Mr. Dalton'^ table exhibited 

 solutions containing 35.3 per cent. ? Why does he not hint at 

 the existence of Sir H. Davy's table, of which he was unques- 

 tionably not Ignorant ? No confidence whatever can be placed 

 m the Doctor's favourite table of the water of ammonia, one of 

 the most important re-agents of the chemist, and one of the 

 most useful preparations of the apothecary. The per centagc 

 of ammonia in the Avater of specific gravity 0.90, is by Sir H 

 Davy's table, 26; a quantity very nearly, if not absolutely, exact.' 

 l^otash soda, and the earths, are merely reprinted from his 

 former edition. 



_ In his introductory remarks on acids, we meet with an asser- 

 tion in the last of the following sentences, which would do dis- 

 credit to the incipient ty,o. " All the acids, at present known, 

 with the exception of three, namely, sulphuretted hydrogen 

 tcliuretted hydrogen, and seleniuretted hydrogen, contain a sup- 

 porter of combustion. By far the greater number of known 

 acids contain oxygen. All acids, therefore, (with the exception 

 of those above named) are combinations of supporters and com- 

 hustihlesr Pray, Dr. Thomson, what is iodic acid ; what i.s 

 rhlonodic acid ; what is chloric acid ; what is Count Stadion's 

 perch one acid ? Where is their combustible element ' 

 We do not find it among any, or all, of your combustibles. 

 I hese acids result from the union of your mefe supportors ; and 

 in their formation combustion takes 'place, without one of your 

 combustibles. The Doctor's remarks on acidity, indoed, "like 



* Si/Ktcm, II., p. 28. 



