ELEMENTS OF MATERIA MEDICA,

denominated extractive. It is tJje presence of this substance which enablessolution of impure hesperidin to form a reddish-brown precipitate with the piron. It frequently contains traces of gallic acid. -.

. . 0 f cilT K

2. IjF.mon Juice. —According to Proust, lemon juice consisi tpa ter,acid, 1'77 ; malic acid, gum, and bitter extractive, 0'72; an jjg- er ent97ol. Lime juice contains the same ingredients, in somewhat 0 (proportions: the quantity of citric acid in it is larger, whilemucilage, &c. is less. . bT Sch*l*

Citric Acid (Acidum Citricum ).—First procured in the solid state, m 17»is found in many acid ‘mii-ee r—” ' found. vV ' 1 "

Bird C'found

_.....yiuMin mrncMm).—-First procured in the solid state, m 1 COIUU n,»-.,

It is found in many acid juices of fruits usually free, but sometimes m vvitl*

with either potash or lime. Besides the fruits of the genus Citrus , it . cherO’little or no malic acid, in the fruits of Dulcamara, Dog-rose, Cranberry, , j„ th e

and Whortleberry. Mixed with an equal quantity of malic acid, it is y an iarind l£Gooseberry, Red Currant, Strawberry, Raspberry , Cherry, &c. In t,eexists with both malic and tartaric acids (see p. 1161). , r t rh 0111 '

Citric acid crystallizes in colourless, odourless, very sour, transparent, s £ vv )n>seboidal prisms, whose extremities are terminated by four trapezoidal fae ps > U

primary form is the right rhombic prism. Crystallized citric acid becomes ^ . £ wexposure to a moist atmosphere, though Dumas and other French chemists ^ paf (sbe unalterable by the air. According to Vauquelin it is soluble in S ,T’ inc/nio^of cold and fifty of boiling water. The solution is strongly acid, and beco ^ II sby keeping. Crystallized citric acid is much less soluble in alcohol than m By

sp. gr. is 1 617. When heated to about 212° F. it fuses into a limpid *4^ citri^distillation it gives two pyrogenous acids. One of these, called pyrocitnc^ jjj ()3;acid, was discovered by Lassaigne, arid consists, according to Dumas, ot^ first-the other, termed citricic acid, was discovered by Baup, and is isomeric w ol ]uc e “'

During the operation, acetone (pyroacetic spirit) and much carbonic Uith ?-

Heated with potash to about 390 tf , it is converted into oxalic acid. Trca t j c ac'“of vitriol, it evolves sulphurous acid, carbonic acid, carbonic oxide, anHeated with nitric acid, it becomes oxalic acid. . . eSC esS , 1,0

The characteristics of citric acid are as follows:—It yields, when added m ^ £)i ce sSprecipitate with lime-water. It does not yield a crystalline precipitate wbe wa tet. aof it is added to a solution of carbonate of potash. It yields, with h_a r J r urI) ish ewhite precipitate ( citrate of baryta). With a solution of acetate of lead ‘f ? a doU^ 6

a white nreeiriitatn t™*—-■* 1 ” soluble in imnu*™ r..—-s wit . a

--j ->

f .... r aK ^curaie oj Baryta), With a solution of acetate of lea

a white precipitate (citrate of lead), soluble in ammonia, which forms wit J uC es *salt (ammoniacal citrate of lead). With a solution of nitrate of silver it P ^,[,8 upjwhite precipitate (citrate of silver), which, when heated, becomes brown, c0i fse'ldeflagrates, discharges white fumes, and leaves an abundant, ash-g re 7’fibrous, crumbly residue, which by heat becomes pure silver.

Citric acid has the following composition :—

Carbon .... 4Hydrogen . 2Oxygen .. 4

Anhydrous (citric acid S 1

Atoms. Eq.Wt. PerCent.

* -21. 41-38

2 . 3 44

22.55’18

Crystals by cooling a Solutionsaturated at 212°.

. 58

. 100-00

. , , Atoms .Anhydrous; .citric acid J 1 • •Water .... i

Eq.Wt.58 ..

• 9 .

Per Cent.

.... 86-57

Atoms. Eq-^

1.58

1 £. 12

Crystallized?citric acid $ .

... 67 ...

1 . 70

pert

100-f

, ... .UftJ'UU ... /V " _'

| vivucttuia } _ _ '

----- 1 '

Physiological Effects and Uses. 1. Of the Lemon 1 ^ Ill0 reLemon peel is a grateful stomachic and aromatic. It is emplo ) e ^ c0 iras a flavouring ingredient than lor its own jiroper effects. Ustituent of the infusum gentiarue compositum (p. 896), and of is al1

aurantii compositum. Candied lemon peel (cortex limonum C0M - ona ry-agreeable stomachic, and is employed as a dessert and in confectio2. Of Oil of Lemons. —Oil or essence of lemons possesses thelant properties of the milder volatile oils, and is denominated ctive and diaphoretic. In full doses it is said to be apt to occasion