?9l© Dr, Thomson's Answer to the Review of the [April, 



paper, I did not allude to these estimates. I can make allow- 

 ance for errors even in a good paper. If this were not made, 

 what chemical paper would be entitled to praise? Where is tlie 

 chemist to be found who has not very frequently fallen into 

 analytical mistakes ? 



20. The sneers at my account of amaionia could not have 

 come from any writer of the smallest candour. I do not attempt 

 to reconcile the discordant statements. My own of course are 

 those which I consider as nearest the truth. Even they would 

 require to be re-examined. The experiments were made 20 

 years ago, when neither my weights nor my measures were so 

 accurate as they are at present. 



21. The Reviewer is quite indignant that Ihave given Mr, 

 Dalton's table of the strength of sulphuric acid, instead of Dr. 

 Ure's. — (P. 153.) I consider Dalton's, as far as it goes, as the 

 best of the two. To a practical chemist, such a table is in fact 

 of veiy little use. I find it of none, except in the rare case of 

 having a dilute acid by me. My method of proceeding is this : 

 I keep by me a few pounds of sulphuric acid, which I have puri- 

 fied by distillation, and concentrated as far as possible. Such 

 acid has the specific gravity 1-8447, and is composed of 5 real 

 acid and 1*1 25 water; consequently 6-1 grainsof it contain exactly 

 5 grains of true acid. I can weigh the exact quantity of this 

 acid wanted with as little trouble as of diluted acid ; I after- 

 wards dilute this portion at pleasure. Indeed I have a glass 

 measure graduated to grains, by which I can measure the 

 quantity of acid when minute precision is not wanted. A table 

 similar to that of Dr. Ure's, we find of no use in my laboratory. 



22. The sneer about lampic acid (p. 153) had better have been 

 omitted, Mr. Daniell having himself acknowledged that this acid 

 is merely the acetic, and consequently verified my opinion. 



23. I do not believe that in the whole history of chemistry any 

 thing can be pointed out more uncandid or unjust than the 

 Reviewer's remarks upon my paper on Oxalic Acid, published in 

 the Philosophical Transactions for 1807. I did not succeed in 

 ascertaining the exact proportion of water contained in this acid, 

 my method (simply heating the acid on a sand-bath) not being 

 capable of separating the whole water. The consequence of this 

 was, that my oxalic acid contained water, and of course my data 

 for determining the composition of the oxalates being wrong, 

 their composition is inaccurately stated in my paper. To cor- 

 rect the error it would be necessary to subtract the portion of 

 water which I allowed to remain in the acid. If the Reviewer 

 does so, he will find my results tolerable approximations. 



The value of the paper does not depend upon these numerical 

 analyses. It contams a great deal of matter, of which I have 

 uniformly availed myself in all the editions of my System pub- 

 lished since 1807, I may mention here that Berard wrote a. 



