ARSENIOUS ACID 217 



not. After 12 hours the furnace is allowed to cool, provided the probe-wires show 

 that the sublimation is over. The cylinders are then lifted off, and the arsenious 

 glass is detached from their inner surface. According to the quality of the poison- 

 flour, it yields from |ths to ^ths of its weight of the glass or enamel. Should any 

 dark particles of metallic arsenic be intermixed with the glass, a fresh sublimation 

 must be had recourse to. 



In these operations, if any sulphur is present it is converted into sulphurous acid, 

 which escapes through the chimney, while the arsenious acid is condensed in proper 

 chambers, placed in the flues to receive it. Freshly prepared arsenious acid is a 

 perfectly transparent solid mass; but by exposure it becomes transformed into an 

 opaque body resembling porcelain. 



White arsenic is extensively xisod in the preparation of various pigments, as the 

 bisulphide, or realgar, the terstdphidc, or orpiment, and also in the mineral greens 

 used by paper-stainers. It has been stated that paper stained with the arsenical 

 greens is injurious to health. Very much has been said on this subject ; but the 

 following remarks by Mr. Alfred Fletcher appear to settle the question : ' Now, it is 

 stated that in a medical work an instance is noted in which injury has been received 

 by those living in rooms decorated with these colours : surely, were the proximity of 

 such materials injurious, it would not be necessary to search in recondite books for 

 the registry of isolated cases. The fact of the large extent to which such materials 

 have always been employed is a sufficient proof that there is no danger attending 

 their use ; moreover, workmen who have been daily employed for many years in manu- 

 facturing large quantities of these colours, under the necessity of constantly handling 

 them, are in the regular enjoyment of perfect health, though exposed also to the 

 general influences of a chemical factory. Let blame be laid at the right door, and let 

 the public be assured that it is not the looking at cheerful walls, the fingering of 

 brightly ornamented books, nor the wearing of tastefully coloured clothing, that will 

 hurt them, but the dwelling in ill-ventilated rooms.' 



Arsenite of Copper. Scheele's green is a combination of arsenious acid with oxide of 

 copper, or an arscnite of copper. See SCHEELE'S GREEN. 



ARSENIC, POISONING BY. This poison is so commonly the cause of death, by 

 accident and by design, that it is important to name an antidote which has been em- 

 ployed with very great success. 



This is the hydrated peroxide of iron. This preparation has no action on the 

 system, and it may therefore be administered as largely and as quickly as possible. 

 The following statement will render the action of this hydrated salt intelligible. 

 When hydrated peroxide of iron is mixed in a thin paste with the solution of arse- 

 nious acid, this disappears, bcingchanged into arsenic acid (a far less active oxide), and 

 the iron into protoxide, 2Fe 2 O 3 and As O 3 , producing 4Fe + As O 5 . The hydrated 

 peroxide of iron may be made in a few minutes by adding carbonate of soda to 

 any salt of the red oxide of iron (perchloride, acetate, &c.). It need not be washed, 

 as the liquor contains only a salt of soda, which would be, if not beneficial, certainly 

 not injurious. Kane. 



Detection of Arsenic in Cases of Poisoning. 



Arsenious acid, which is almost always tho form in which the arsenic has entered 

 the system, possesses the power of preventing the putrefaction of animal substances ; 

 and hence the bodies of persons that have been poisoned by it do not readily putrefy. 

 The arsenious acid combines with the fatty and albuminous tissues to form solid 

 compounds, which are not susceptible of alteration under ordinary circumstances. 

 It hence has frequently occurred that the bodies of persons poisoned by arsenic 

 have been found, long after death, scarcely at all decomposed ; and even where the 

 general mass of the body had completely disappeared, the stomach and intestines 

 had remained preserved by the arsenious acid which had combined with them, and 

 by its detection the crimes committed many years before have been brought to light 

 and punished. Kane. 



The presence of arsenic may bo determined by one of the following methods : 



1. Portions of the contents of the stomach or bowels being gently heated in a glass 

 tube, open at both ends, the arsenic, if in any quantity, will be sublimed, and collected 

 as minute brilliant octahedrons of arsenious acid. 



2. Or if the ignition is effected in a tube closed at one end, metallic arsenic sub- 

 limes, forming a stoel-groy coat, and emitting a strong smell of garlic. 



3. Ammoniacal Nitrate of Silver produces a canary-yellow precipitate of arsenite of 

 silver in a solution of arsenious acid. The tribasic phosphate of soda produces a 



