230 Scientific Intelligence. -[Marcn, 
renewed more speedily and more perfectly when the part is 
covered up from the action of the air than when it is exposed to 
that action. These facts, stated by Mr. Keith, seem to leave no 
doubt that the use of the epidermis in plants is the very same as 
in animals: that it is formed for the express purpose of protecting 
the parts below it, and that the analogy between the animal and 
vegetable epidermis is complete.—(Linnean Trans. xii. 6.) 
X. Method of procuring Meconic Acid, 
The infusion of opium, from which the morphia had been pre- 
cipitated by means of ammonia, was evaporated to the consist- 
ence of a syrup, and left in a state of rest; but no crystals 
would form in it.* It was then diluted with 16 ounces of water, 
and mixed with one ounce of caustic ammonia. As no precipi- 
tate appeared after the interval of an hour, the liquid was heated 
to drive off the excess of ammonia. When heated to the tem- 
perature of 122°, it became muddy, and 15 gr. of impure 
morphia were precipitated. 
The liquid being freed from this precipitate and from the 
excess of ammonia, muriate of barytes was poured into it as long 
as any precipitate fell. The precipitate, being collected and 
dried, Wighed seven drams, and was Sertiirner’s meconate of 
barytes. ‘To obtain the meconic acid from this salt, M. Chou- 
lant triturated it in a mortar, with its own weight of glassy 
boracic acid. This mixture being put into a small glass flask, 
which was surrounded with sand im a sand pot in the usual man- 
ner, and the heat being gradually raised, the meconic acid 
sublimed in the state of fine white scales, or plates. 
XI. Properties of Meconie Acid. 
It has a strong sour taste, which leaves behind it an impres- 
sion of bitterness. 
It dissolves readily in water, alcohol, and ether. 
It reddens the greater number of vegetable blues, and changes 
the solutions of iron to a cherry-red colour. When these solu- 
tions are heated, the iron is precipitated in the state of protoxide. 
The meconiates, examined by Choulant, are the following : 
(1.) Meconiate of Potash.—It crystallizes in four-sided tables, 
is soluble in twice its weight of water, and is composed of 
Meconic acid ........ A AE A Ss omaate. 
P GRAS oe ctad cus py SRR «| RYT 
Water, nies i Nea 13 
100 
{t is destroyed by heat. 
(2.) Meconiate of Soda.—Crystallizes in soft prisms. Soluble 
in five times its weight of water. Seems toeffloresce. Decom- 
posed by heat. Its constituents are, 
* See the notices on Morphia in the last Number, p. 153, 
