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



sion. What I state is, " it would be better to adopt the Lon- 

 don process of using equal weights of nitre and sulphuric acid/' 

 but this is the only part of it which 1 meant to adopt. Indeed 

 it would be singular if I had done more, for in my Experimental 

 Examination, I have stated that I never found any sulphuric 

 acid in the product. It is also true that the nitric acid obtained 

 by using the proportions of the London Pharmacopoeia is not 

 quite colourless, but it is very nearly so : scarcely any difference 

 can be perceived between it and that procured by your method, 

 and it is quite as strong, or indeed rather stronger. With re- 

 spect to the colour of the acid, you correctly inform me that 

 when nitrous acid is diluted with water, it becomes of a rich 

 green colour ; but I can by no means admit the accuracy of your 

 intimation, that it requires " free exposure to the air" to render 

 it pale ; for without it is kept quite closely stopped ; and in a 

 bottle but little larger than requisite to hold it, the very act of 

 opening the bottle occasionally is sufficient to admit of the escape 

 of the deutoxide of azote, and to render the acid colourless. 



As you have spoken of the economy of the process for ob- 

 taining acetic acid, it is evident that this is a consideration 

 which has not escaped your notice, although I have shown 

 that you have not been successful in the practice of it. I shall 

 now briefly state the comparative costs of obtaining nitric acid 

 by employing one proportion and two proportions of sulphuric 

 acid ; and also by your method in winch one proportion and a 

 half is used. The numbers representing sulphuric acid and nitre 

 are respectively Gl-32 and 12b - 6. For the sake of round num- 

 bers, I shall assume that they are as i to 2. 



I distilled a mixture of 24 parts of nitre and 16 of sulphuric 

 acid. In four hours, from the commencement of the operation, 

 the ingredients were in complete fusion, and no uncondensible 

 gas came over. In about five hours, a little gas was evolved, 

 the acid dropping only about three times in a minute. In two 

 hours more, I weighed the product, and found it almost exactly 

 1 1 parts ; in eight hours from the commencement of the opera- 

 tion gas came over plentifully, and the acid dropped once in about 

 five minutes. The whole product weighed 13 - 4 parts. It was 

 of a red colour, but its specific gravity I accidentally have not 

 noted. The pipe of the tubulated receiver almost touched the 

 bottom of the bottle, so that any gas which was evolved in the 

 latter part of the operation passed through the pale fluid acid 

 first distilled. 



On repeating this experiment, but without causing the pipe 

 of the tubulated receiver to dip into the first obtained product, 

 I procured 13-(j parts of product. This acid was of a red colour; 

 its specific gravity was 1534 ; and on making the experiment 

 for the third time, but with the pipe of the tubulated receiver 

 arranged as in the first experiment, I procured 13-7 parts of 

 acid ; the colour was red, and its specific gravity 1540. 



