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SOD

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is soluble in 20 parts-of water at 60°, and in b parts at 212". Incompati-ble Substances. It is decomposed by acids ; potass; by the sulphates andmuriates of the earths, and by those of ammonia. Medicinal Uses. Itis only applied in the form of powder mixed with 8 or 10 parts of honey,as a detergent linctus in aphthse, &c. The Chinese employ it in imflam-matory sore throats ; for which purpose they first reduce it to an extreme-ly fine powder, and then blow it through a reed upon the inflamed sur-face. Officinal Preparations. Mel Boracis. L. Adulterations.Alum, and/used muriate of soda, are substances with which it is some-times sophisticated ; to discover which, dissolve it in distilled water, andafter saturating the excess of the base with nitric acid, assay the solutionwith nitrate of bary tes and nitrate of silver.

SOD.E SUB-CARBONAS. L.E.D.

Sub-carbonate of Soda.Qualities. Form, octohedrons, truncated at the summits of the pyramids ; it effloresces when exposed to the air, and at 150° Fah. undergoeswatery fusion, its crystals containing as much as seven proportionsof water ; Taste, mild, alkalescent- Chemical Composition. Soda29-5—carbonic acid 20-7. Solubility. It is soluble in two parts ofwater at 60°, and in considerably less than its weight of boiling water ;it is insoluble in alcohol. Incompatible Substances are enumeratedunder Potassx Carbonas. Med. Uses, are similar to those of the sub-carbonate of potass, but it is preferable to it for internal use, as beingmore mild and less nauseous ; and moreover Fourcroy states it as hisopinion that soda is more eligible for mpdicinal purposes than potass, onaccount of its analogy with animal substances, which always contain it,while on the contrary, no portion of potass is found in them. Sir GilbertBlane assumes an opposite opinion, and observes that, as far as he canjudge of the comparative powers of the two fixed alkalies, he shouldgreatly prefer Potass to Soda, as a remedy for gravel, one reason of whichhe thinks may be found in the fact that the Soda is an element of the ani-mal fluids, since it enters largely into the composition of bile, so that itis more likely to be arrested in the course of the circulation and divertedfrom the urinary organs. A gentleman, says Sir Gilbert, who was sub-ject to frequent fits of gravel, and in the habit of making experiments onihe small concretions which he passed, found that Soda dissolved them,but that Potass did not; nevertheless he experienced sensible relief, andeven temporary cure, from the internal use of the latter alkali, but nobenefit from the former. Are then the absorbents more disposed to takeup soda than potass ? The results of experience do not appear to sanc-tion such a conclusion. Forms of Exhibition. It may be administeredin solution, in an electuary, or in pills; when exhibited in the latterform, it must be previously deprived of its water of crystallization, (Sod<eSub-carbonas exsiccata. L.) or the pills will fall into powder as they dry ;unless where the water of crystallization is essential to the formation of

the pill, as to that of Pill : Ferri comp. Dose, gr. x to 3j, twice orthrice a day. See Form. 23, 143,144.

SODjE SULPHAS. L.E.D.

J\~atron Vitriolatum, P.L. 1787. Sal Catharticus Glauberi. P.L. 1745.Qualities. Form, transparent prismatic crystals, which effloresce :when exposed to heat, they undergo watery fusion, that is. they melt in