EQUIVALENT PROPORTIONS OF CONCRETE CITRIC ACID AND LEMON JUICE, NECESSARY FOR THE NEUTRALIZATION OF ALKALINE SALTS.
┌──────────────────────┬──────────────────────┬───────────────────────┐ │ Citric Acid. │ Lemon Juice. │A Scruple of Alkalies. │ ├──────────────────────┼──────────────────────┼───────────────────────┤ │ grs. x. │ fʒiij │ Carbonate of Potass. │ ├──────────────────────┼──────────────────────┼───────────────────────┤ │ grs. xv. │ fʒiiij │ Sub-Carbonate of │ │ │ │ Potass. │ ├──────────────────────┼──────────────────────┼───────────────────────┤ │ grs. xxv. │ fʒvij │ Sub-Carbonate of │ │ │ │ Ammonia. │ └──────────────────────┴──────────────────────┴───────────────────────┘
These alkaline citrates are decomposed by the _oxalic_, _tartaric_, and the stronger _mineral acids_, and by the solutions of _lime_ and _barytes_. _Form. 107, 123, 137, 168._
Citric acid decomposes the following salts, _viz._ _The Alkaline, Earthy, and Metallic Carbonates_; _the Alkaline and Metallic Acetates_; _the Sulphurets of Earths and Alkalies, and Alkaline Soaps_. It is also incompatible with _Tartrate of Potass_, which it converts into citrate and super-tartrate of potass. It curdles the milk of most animals, but it does not produce that effect on human milk, whether applied hot or cold. ADULTERATIONS. _Tartaric Acid_, with which it is sometimes mixed, may be detected by adding to the solution an excess _of Potass_, which will instantly form with it an insoluble super-tartrate, and precipitate in granular crystals, or, if a little of the suspected acid be saturated with potass, and then boiled with a dilute solution of muriate of Platinum, if tartaric acid be present, a black protoxide of Platinum will be precipitated. If we add the tartrate of potass for this purpose, we may be deceived, for the citric acid, by neutralizing a portion of its base, will convert the remainder into super-tartrate. See _Potassæ Tartras_. _Sulphuric Acid_ is known by the acetate of lead producing a precipitate, insoluble in nitric acid. _Muriatic Acid_ may be discovered in the same manner, substituting only an acidulous solution of nitrate of silver for the acetate of lead. The presence of _Oxalic Acid_ may be inferred, if the solution, when added to that of sulphate of lime, produce a precipitate. Malic acid has the power of precipitating silver, mercury, and lead, from their solutions in nitric acid, but no doubt or difficulty can arise from this circumstance, for the fact of its forming a soluble salt with lime will prevent every chance of accidental intrusion, and its price at once secures us against its fraudulent introduction; it might moreover be easily detected by throwing the suspected precipitate upon burning coals, when it would be decomposed. Where the presence of _lime_ is suspected, it may be known by dissolving some of the crystals in water, saturating the solution with ammonia, and then treating it with the oxalate of that alkali, which, if lime be present, will immediately separate it in a palpable form. The juices of many other fruits besides the lemon and lime, will furnish the citric acid in abundance, and may be obtained from them by a similar process; e. g. VACCINIUM OXYCOCCUS, the _Cranberry_; PRUNUS PADUS, the _Bird’s Cherry_; DULCAMARA SOLANUM, the berry of the _Nightshade_; CYNOSBATUS, vel ROSA CANINA, the hep or fruit of the _Wild Briar_. There are many plants whose juices contain combinations of the _Citric_ and _Malic_ acids in considerable abundance, such as FRAGARIA VESCA, the _Wood Strawberry_, and the common _Raspberry_; RIBES RUBRUM the _Red Gooseberry_; VACCINIUM MYRTILLUS, the _Bilberry_; CRATÆGUS ARIA, the _Hawthorn_; PRUNUS CERASUS, the _Black Cherry_, &c. This fact is interesting, since the juices of such fruits have been long known to possess the property of dissolving the _tartareous_ incrustations on the teeth.