'220 ARSENIOUS ACID 



fluids and solids suspected to contain arsenic, may bo prepared for this purpose by 

 boiling them for half an hour with a little hydrochloric acid ; solid matters being cut 

 into small shreds, water being added in sufficient quantity to let the ebullition go on 

 quietly, and care being taken to continue the boiling until the solids are either dis- 

 solved, as generally happens, or are reduced to a state of minute division. 



The method of Eeinsch is exceedingly delicate, for it is adequate to detect a 

 250,000th part of arsenic in a fluid. It is also perfeet in another respect : it does not 

 leave any arsenic in the subject of analysis ; none, at least, which can be detected by 

 any other means, even by the most delicate process yet proposed, that of Mr. 

 Marsh. 



Cut the copper on which the arsenic is deposited into small chips, so that they 

 may be easily packed in the bottom of a small glass tube, and apply a low red heat. 

 A white crystalline powder sublimes ; and if this bo examined in the sunshino, or 

 with a candle near it, a magnifier of four or five powers will enable the observer to 

 distinguish the equilateral triangles composing the facets of the octahedral crystals, 

 which are formed by arsonioiis acid when it sublimes. Sometimes the three equal 

 angles, composing a corner of the octahedron, may be seen by turning the glass in 

 various directions. If triangular facets cannot be distinguished, owing to the minute- 

 ness of the crystals, then shake out the copper chips, close the open end of the tube 

 with the finger, and heat the sublimed powder over a very minute spirit-lamp flame, 

 chasing it up and down the tube till crystals of adequate size are formed. Next boil 

 a little distilled water in the tube over the part where the crystalline powder is 

 collected; and when the solution is cold, divide it into three parts, to be tested 

 with ammoniacal nitrate of silver, ammoniacal sulphate of copper, and sulphuretted 

 hydrogen, either in the state of gas or dissolved in water. 



8. Fleitmann's Test. If a solution containing arsenic be mixed with a largo excess 

 of concentrated solution of potassa, and boiled with fragments of granulated zinc, 

 arseniuretted hydrogen is evolved, and may be easily recognised by allowing it to 

 pass on to a piece of filter paper spotted over with solution of nitrate of silver. These 

 spots assume a purplish-black colour, even when a small quantity of arsenic is present. 

 This experiment may be performed in a small flask, furnished with a perforated 

 cork carrying a piece of glass tube of about 1 inch diameter. It will be observed 

 that this test servos to distinguish arsenic from antimony. 



The following remarks on the Toxicological Discovery of Arsenic deserve atten- 

 tion : 



' This active and easily administered poison is fortunately one of those most easily 

 and certainly discovered ; but the processes require great precaution to prevent mis- 

 taken inferences : if due care is taken, arsenic can be found after any lapse of time, as 

 well as after the most complete putrefaction of the animal-remains. The longest time 

 after which it has been discovered by myself is eight years, which was the case of an 

 infant ; nothing but the bones of the skeleton remained, the coffin was full of earth, 

 and large roots of a tree had grown through it. The metal was obtained from the 

 bones, and in the earth immediately below where the stomach had existed. Many 

 cases have occurred in my experience, where one, two, three, four, and five years 

 have elapsed ; in one case, after fourteen months, where the body of a boy had been 

 floating in a coffin full of water. The poison is given in one of three states, white 

 arsenious acid, yellow sulphuret (" orpiment "), or " realgar," red sulphurct of arsenic ; 

 and it is worthy of notice that putrefaction will turn either white or red into yellow, 

 but will never turn yellow into either white or red ; this is owing to the hydrosul- 

 phuret of ammonia disengaged during decomposition. 



'Modern toxicologists have abandoned all the old processes for the detection of this 

 poison, and have adopted one of two, which have been found more expeditious, as well 

 as more certain. The first was proposed by Marsh, of Woolwich: it is founded upon 

 the principle that nascent hydrogen will absorb and carry off any arsenic which may 

 be present, as arseniuretted hydrogen ; but as I prefer the principle first proposed by 

 Roinsch, and have always acted upon it, I shall confine my description to the pro- 

 cesses founded upon it. The principle is this : arsenic mixed or combined with any 

 organic matter will, if boiled with pure hydrochloric acid and metallic copper, be de- 

 posited upon the copper ; but as this depositing property is also possessed by mercury, 

 gc antimony, bismuth, lead, and tellurium, 



, '. . subsequent operations are required to 



( " .^ ..^^ discriminate between the deposits. I 



V ' ' ^^ take pieces of copper wire, about No. 13 



size, and 2 inches long ; these I hammer upon a polished plane with a polished hammer, 

 for half their length (fig. 85), and having brought the suspected matters to a state of 

 dryness, and boiled the copper blade in the pure hydrochloric acid, to prove that it 

 contains no metal capable of depositing, I introduce a portion of the suspected matter 



