26 Mr. Phillips's Reply to Dr. Hope. [July, 



You assign as reasons for employing the proportions of 16 

 parts of sulphuric acid to 24 of nitre, first, " that the prescribed 

 quantity of sulphuric acid is required, and proves sufficient to 

 detach the whole of the acid from the nitre; secondly, the acid 

 thus procured is of great strength, and so free from sulphuric 

 acid, as to render the second distillation enjoined by the London 

 College altogether unnecessary for ordinary purposes." Now in 

 reply to the^e statements, I would observe, first, that in my 

 opinion, and founded upon experiment, the quantity of sulphuric 

 acid is not required to detach the whole of the acid from the 

 nitre ; and, secondly, that although it does detach it, yet only 

 three-fourths are obtained when the sulphuric acid is of the 

 greatest strength, on account of the deficiency of water in it to 

 condense the nitric acid. 



I mixed in a retort 100 parts of nitre and 50*6 parts of sulphu- 

 ric acid, of specific gravity 18435, which are equivalent to about 

 48'87 of sulphuric acid of the greatest procurable density ; the 

 sulphate of potash obtained weighed 86-2 parts, exceeding only 

 by 0"2 the quantity mentioned on the scale. Bypassing the gas 

 liberated towards the end of the operation through water, I 

 obtained nitric acid equivalent to 46 - 2 solvent power instead ot 

 50, as denoted by the scale. From this experiment I contend 

 that it is not requisite to employ more sulphuric acid than is 

 required to convert the nitrate into sulphate of potash. It is 

 indeed true that about l-12th of the product is lost in the opera-, 

 tion. Now I will even grant for a moment that you obtain 15 

 parts of nitric acid of the greatest density and solvent power 

 from 24 parts of nitre, instead of 15 of red nitrous acid, as you 

 state ; these 24 parts of nitre are capable of yielding 17 of such 

 acid, and it is, therefore, evident that, although you decompose 

 the whole of the nitre, from the want of water to condense the 

 product you lose more than one-eighth of it. 



In one part of your remarks, you say, " Permit me to observe 

 that most of your objections to the formulas apply to the relative 

 quantities of the materials employed, and rest upon these quanti- 

 ties deviating from the proportions of combination stated in Dr. 

 Wollaston's table of chemical equivalents. 1 apprehend, however, 

 that you have made an application of this beautiful and valuable 

 contrivance which its very ingenious 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 quantities of the substances to be employed 

 when decompositions are to be effected, particularly by single 

 affinity." I think you must have overlooked a part of Dr. Wol- 

 laston's memoir which refers to the very subject under discus- 

 sion, and in which the number that he employs in describing 

 the relative quantities of sulphuric acid and nitre to be used are 

 taken from the scale which he had been describing. " In the 

 distillation of nitric acid from nitre," says Dr. Wollaston, " the 



