386 Prof. Christison on the Poisonous Properties of Hemlock, 



tilled anew, it is simply reproduced without any material change 

 except some loss of strength. But if it be previously neutralized 

 with an acid, such as the sulphuric, the volatile poisonous prin- 

 ciple becomes fixed, and water alone is distilled over. The resi- 

 duum consists of sulphate of conia, sulphate of ammonia, and 

 resinoid matter, the resin and ammonia being produced by de- 

 composition of a part of the conia under the operation of heat 

 and the access of air. In order to obtain the conia, the mass is 

 subjected to a mixture of two parts of rectified spirit and one of 

 sulphuric ether, which leaves the sulphate of ammonia undissolv- 

 ed. And then, the ether and alcohol being distilled carefully off, 

 the remaining sulphate of conia is heated gently with a little wa- 

 ter and caustic potassa ; upon which there is obtained in the re- 

 ceiver a watery solution of conia in the lower part, and floating 

 on this a layer of nearly pure conia, colourless, transparent, and 

 presenting the physical appearance of an oil. 



In this state the conia contains a little ammonia and a fourth 

 of its weight of water, the latter of which may be removed by 

 chloride of calcium, and the former by exposing it to the air- 

 pump vacuum so long as bubbles of gas escape. By neither pro- 

 cess of purification, however, is the physical appearance of the 

 conia materially changed. 



Conia thus obtained has the appearance of a colourless vola- 

 tile oil. It is lighter than water, of a very powerful diffusible 

 repulsive odour, somewhat like that of hemlock itself, and intense- 

 ly acrid to the taste. It has a strong alkaline action on reddened 

 litmus or turmeric. It is readily soluble in diluted acids, which 

 it neutralizes ; but its salts have not yet been obtained in the 

 crystalline form. It is sparingly soluble in water, to which it 

 imparts its odour and taste. It also combines with about a 

 fourth of its weight of water to form a hydrate of conia. Both 

 this hydrate and the watery solution possess the property of be- 

 coming opaque when slightly heated, and recovering their trans- 

 parency on being again cooltd. When exposed to the air it 



