]^: Dr, Hope's Remarks on Mr. Phillips's Analj/sis [March^ 



combination stated in Dr. Wollaston's table of chemical equiva- 

 lents. I apprehend, however, that you have made an application 

 of this beautiful and valuable contrivance which its very inge- 

 nious author never contemplated, and could not now sanction ; 

 for though that table displays the proportions in which different 

 substances combine, it by no means displays the relative quan- 

 tities of the substances to be employed, when decompositions 

 are to be effected, particularly by single affinity. It has been 

 long known to chemists that to achieve the complete decompo- 

 sition of any quantity of a compound, an excess of the decom- 

 posing material is either absolutely necessary, or very useful, by 

 accelerating the operation. 



Were I not addressing myself to a person thoroughly versed 

 in the science of chemistry, it would be easy to explain in detail 

 the reason of the circumstance ; but it will bo sufficient to 

 remark that this excess is in some cases indispensable from the 

 disposition of the decomposing agent to form a super or bicom- 

 pound with the ingredient to which it is to attach itself, as in 

 the decomposition of nitrates and muriates of alkalies by sulphu- 

 ric acid to be immediately brought into view ; and also when the 

 substances are in the state of dry powder, in order that each' 

 particle of the compound may fully and freely encounter those 

 which are to act upon it. 



, The reader who may think it worth his while to peruse these 

 observations is particularly requested to direct his attention to 

 your critique commencing in p. 58 of the first number of the 

 Annals of Philosophy, and to read in succession the different 

 articles to which a reply is now to be given. 



Acidum Aceticum Forte is the first substance of which you 

 take notice, and your objection to the formula for its preparation 

 is, that the quani:ities of the salts employed are not such as are 

 required for mutual decomposition. It is unquestionably true 

 that the sulphate of iron contains more sulphuric acid than is 

 required to saturate the oxide of lead in the acetate, but it is of 

 advantage to employ this excess. It facilitates greatly the dis- 

 engagement of the acetic acid, and renders it unnecessary to 

 raise the temperature to so high a pitch as would otherwise be 

 required, by which means the empyreuma, unavoidable in an 

 elevated temperature, is in a great measure prevented ; hence at 

 the trifling expence of an additional quantity of the sulphate of 

 iron, and of an increased size of utensil, there is a saving of time 

 and of fuel, and a vast gain in the quahty of the product. The 

 object of this process is to obtain a very strong acid capable of 

 dissolving camphor at a cheaper rate than from acetate of 

 copper. 



Acidum Muriaticum, — Upon the preparation of this substance 

 you remark, that ** Equal quantities of sulphuric acid and com-j 

 mon salt are directed to be employed in the preparation of this 

 acid. It will be seen by Dr. Wollaston's scalethat the requisite 



