1825.] Mr, Hemes on an improved A-er-^pum^t 901^ 



means of charcoal, and I have guarded against it^ 

 extent by subjecting the solution to its action for a very short 

 time, and without the application of heat. I was al 5^0 aware 

 that some fluids are incapable of being decolorized ; and I stated 

 the fact in my paper, without indeed naming them, from motive 

 which may 1 think be understood. o. 



I shall now state a few experiments which are, I think, concluf- 

 sive as to the power of animal charcoal. I dissolved one graitl. 

 of arsenious acid in 600 grains of port wine ; to the solution 

 when cold, I added 100 grains of washed animal charcoal, and 

 agitated the mixture for about two minutes, and then filtered it. 

 The solution was nearly colourless ; I diluted a portion of it with 

 water, and on the addition of a solution of sulphuretted hydrogen, 

 the characteristic yellow colour appeared, although the arsenions 

 acid formed only -j-Vo- ^^ ^^^^ solution. The copper test also 

 readily indicated its presence when of the same strength, aiuj 

 the silver test readily detected the arsenic whea so fai* diluted a« 

 to form only -pg-i-g-g. of the solution; •^i^-«dtav?of{a//ofX^nivx 



I have already admitted that there ai'e (iei^M in' whrcb animal 

 charcoal is powerless; but unless we are to attempt nothing 

 because all cannot be performed, I retain my opinion that it may 

 be useful, and as it decolorizes so deep a coloured fluid as poit 

 wine with facility, little doubt can, 1 think, be entertained of its 

 efficacy upon the less usually intense colo«r-Gf the Auid-conteaAat 

 of the stomach. ; '- «'* ^ SOlif^^up aiiis^soiqedh 



'? There are some other parts of Dr.'Chrfeti^oii'fe p'af^ii^whi^h 

 i^ould require notice if I were entering upon a general discussioin 

 aji to the best tests to be employed ; and I can by no means 

 agree with him that the copper and silver tests " are the two 

 most inaccurate and most fallacious of the common reagents .; " 

 on the contrary, I think, they may be used in many cases w^ith 

 great advantage, especially vvith the precautions and modifica- 

 tions which have been recommended by various chemists. 

 ' 'In concluding these observations, I readily acquit Dr. Chris- 

 tlson ofmtentional misrepresentation, but 1 trust he will repeat 

 the experiments, and candidly state the results, so as to coiu- 

 perisate for jier^arelessne^sxjf iwhiehili^have just caus^ofeo 



cbniplikiu. "J^^ ^*^ ^-' - ' '^ -" ^^^^^ 1 ^/i^r o., , :_ .s^umm 



^ilj f\n&^ ,^iild ymAii yiiji.. /i,;iiil/^i'>/9 ,11^ ^30jjbo'iq U^i laq 

 eiifi wu/l ''.9i£jiqio9'rq ^jid^' .>ii?w> inebnx/dB nxj Jgai -isvlia 

 bamioi isvlig lo sbjioIxfrA W^l^?i XU? 3ji?itqi09iq iajshnudB 



*o ■id§MS^'^^^^"^ f^^^ ^'' improved CoTish'iic'tloh in the Arr-piir^'^*^ 



ff.^or . Ry ^'Jf**- Joseph Henies, Joiner. (With a Plate.Y"';'^^ ; 

 J^UBO sdi 'ffo tlie Editoi-s of the Ajimfs of rhiIosoj)h.i/^^^^^^ g- ^ 

 3m : GENTLEMEN, ,. \ ^ss^O'iq a gqiihfjS Edinburgh, Jt{r^\5^]^Q 



■■'^^M^ attention havibg^beenl called' to' 'the construciion^Qfribe 

 Air-pnmp, during the valuable lectures deHvered in Uie< shoals 



7<; v^tavajj' 



