24 Df\ Chmllson's Reply to Mr. Phillips. [Jutv; 



was, that, if I did not, some critic might accuse me of thinking 

 charcoal necessary for that process. 



I come now to the real subject of dispute between us. The 

 sum of your third criticism is, that I misunderstood your direc- 

 tions, and instead of mixing, actually boiled my fluids with the 

 ivory-black. My reasons for so doing were, that at Paris, my 

 school of instruction in this matter, 1 was taught that coloured 

 liquids required less charcoal for their decolorization at the 

 boiling than at the mean temperature ; — that I believed there 

 were obvious advantages in using as little charcoal as possible ; 

 — and consequently that as some of your directions were given 

 succinctly, and you used in one place the ambiguous i^imdigesty 

 I inferred you meant the charcoal to be applied according to 

 use and wont. 1 was wrong it seems. But as you do not 

 accuse me of wilful error, I cannot understand how it did not 

 occur to you that you were wrong too, — in not giving us igno- 

 rant people more precise directions. 



I confess, however, I was at a loss to imagine what difference 

 this unhappy boiling of my fluids was to make. Animal charcoal 

 possesses the power of absorbing saline as well as colouring 

 matters from solutions ; and cannot, I apprehend, remove the 

 one without also removing the other. From your expression, 

 that my error is fatal to my objection, it appears your opinion 

 is the reverse, although it is not any where stated categorically. 

 As I presume your opinion is founded on strict experiment, I 

 shall not at present dispute the general rule. But assuredly it 

 does not hold with all coloured fluids ; for I find that strong 

 tea, with cream and sugar, containing a grain of arsenic per 

 ounce, parts with most of the arsenic before losing its colour. 



I have not repeated your experiments, because, notwithstand- 

 ing the example of distrust you set me, I am willing to believe 

 them correct. There is one thing, however, I am doubtful 

 about; and that is, the validity of the indication you obtained, 

 in a decolorized solution of arsenic in port-wine, with the cop- 

 per test. For the arsenite of copper is soluble in a small quan- 

 tity of many vegetable acids, and indeed in most vegetable and 

 animal infusions, even though they do not contain a free acid. 

 At the same time a greenish precipitate is really thrown down 

 Eomelimes ; but it is not the arsenite of copper. I suspect your 

 precipitate, therefore, was not the arsenite. 



Nevertheless, although 1 believe your experiments correct, I 

 cannot concede to you the importance claimed for your decolo- 

 rizing process. And my objections are still the following: — 



1. it does not decolorize every Jiuid, — This fact, with all 

 uubmission, I hold to be a material objection. Suppose an 

 analysis has been committed to an inexperienced person [and 

 iiine-tfinths of raedico-legal analyzers are inexperienced], who 



