890 3/r. Phillips^s Remarks on M. Longchamp*s Memoir [Oct. 



are stated to have given the following quantities of sulphate of 

 barytes, when decomposed by means of the nitrate and muriate 

 of barytes : 



By the Nitrate. 



Exper. 1 221-030 



2 217-660 



3 213-109 



4 209-667 



Giving a mean of 215*3665 



By the Muriate, 



Exper. 1 211-277 



2 211-912 



Giving a mean of. 21 1-5945 



" Thus," says M. Longchamp, " 100 parts of the same sul- 

 phuric acid gave 



«' By the nitrate of barytes 215-3665 



By the muriate of barytes 211-6945/' 



and the inference which he deduces from these experiments is, 

 that it is evidently impossible to determine the quantity of real 

 acid which dilute sulphuric acid contains, by means of the salts 

 of barytes. 



A few observations will be sufficient to prove that this infer- 

 ence is unwarranted by the experiments which are supposed to 

 prove its truth, and it will, I think, readily appear, that M. Long- 

 champ's method of performing experiments is radically defective. 

 The difference of the mean results, it will l)e observed, amounts 

 to only 3*7720 parts, whereas the difference of two experiments 

 with the nitrate of barytes, is 11-363 parts; it is, therefore, 

 evident, that one or both of these experiments must be extremely 

 erroneous. Again, if M. Longchamp had made only two expe- 

 riments with the nitrate, as he has with the muriate, and those 

 two had accidentally been the third and fourth stated, the mean 

 would have been 211, -388 sufficiently approximating2l 1 -5945, 

 the mean of the two experiments with the muriate, to have enti- 

 tled the author to have arrived at conclusions diametrically oppo- 

 site to those which he has advanced. 



In order, however, to put the subject to the test of experiment, 

 I diluted some sulphuric acid with a considerable proportion of 

 water, and divided the solution into eight parts. To four of 

 these, solution of nitrate of barytes was added, slightly in excess, 

 and the remaining four were similarly treated with muriate of 

 barytes. The precipitates were washed with distilled water until 

 sulphuric acid produced no effect in it : they were then all slowly 

 dried at the same temperature until they ceased to lose weight. 



