ERYTHRELLIC ACID. 



ESCHAROTICS. 



95< 



caUiueuia, and its premature disappearance la not unfrequently suc- 

 ceeded by dangerous internal disease, as inflammation of the lungs. 



The primary causes of erythema are the friction of contiguous parts, 

 especially in fat persons ; the accumulation of morbid secretions and 

 excretions on the skin, as the matter of the perspiration, of the leuco- 

 rrhioal discharge, of the oatameuia, and of the alvine and urinary evacua- 

 tions, in the adult in the course of other diseases ; and in the infant in 

 consequence of a want of proper ablution. It is also constantly produced 

 by irritating articles of food and drink, and is the sign and the result 

 of a disordered state of the digestive organs. 



In most cases the affection disappears soon after the removal of the 

 cause which produces it by free ablution where it is the result of 

 irritating matters on the skin ; its disappearance ia assisted some- 

 times by the application of an absorbent powder to the inflamed 

 surface, and at other times by the use of a gentle stimulating lotion, as 

 the spirit wash. When the disease is dependent on a disorder of the 

 digestive organs, it can be removed only by the remedies proper for 

 the removal of the stomachic, the hepatic, or the intestinal derange- 

 ment. For the restoration of these organs to their sound condi- 

 tion, the most appropriate remedies are light diet, diaphoretics, the 

 mercurial alteratives in combination with gentle aperients, and 

 the mineral acids as tonics. (Bateman's ' Practical Synopsis of Cuta- 

 neous Diseases ; ' Copland's ' Dictionary of Practical Medicine.') 



EHYTHRELLIC ACID. [ERYTHRIO ACID.] 



ERYTHRIC ACID (C 3 .,H,,0 10 ? ). Erytkrin. This acid was first 

 discovered by Heeren in the Roccella tinctoria, a lichen from which is 

 prepared a colour used in dyeing. It has since been found in other 

 lichens used for the same purpose, and has been particularly examined 

 by Stenhouse and Schunk. From erythric acid are derived Knjtli /> II Ic 

 acid, Picroerythrin, and rylhro-mannite. Orcin is also a derivative, 

 but as it likewise exists ready formed in several of the lichens, and is 

 moreover of considerable importance, it will be treated of in a separate 

 article. [LICHENS, COLOURING MATTERS OF.] 



Erythric acid may be readily obtained from the RucceVa in which it 

 exists to the extent of ten or twelve per cent., by digesting that 

 lichen in water for a 'few hours, and then adding slaked lime. The 

 acid unites with the'lime, forming a salt that dissolves in the water. 

 To the strained liquor hydrochloric acid is added, which precipitates 

 the erythric acid in a gelatinous state. Collected on a filter, washed 

 with a little cold water, the water removed by pressure, and the cake 

 dissolved in warm alcohol, the acid is obtained on cooling in stellate 

 groups of acicular crystals. The acid must not be boiled with alcohol, 

 or a compound ether is formed. 



Erythyric acid is colourless, tasteless, and odourless ; it is soluble in 

 140 parts of boiling water, almost insoluble in cold water, and tolerably 

 soluble in warm alcohol or ether. By beat it is decomposed, orciu at 

 the same time being produced as a sublimate. Long boiling with 

 water converts erythric acid into picroerythrin, with evolution of 

 carbonic acid, 



C.iH,,0,, + 4HO = 2C0 2 +C 30 H., 1(1 



Erythric acid. 



Picroerythrin. 



Erythric acid is precipitated by subacetate of lead ; the compound 

 formed contains fiO'1'2 per cent, of oxide of lead. 



Erythric acid dissolves in ammonia, yielding on exposure to air a 

 deep purplish-red solution. It also dissolves in the fixed alkalies and 

 their carbonates, from which solutions stronger acids reprecipitate it 

 unchanged. Continued ebullition with baryta or lime coverts it into 

 orcin, with production of a carbonate of the base : 



Erythric acid. 



Orcin. 



Erythrdlic acid ia produced to a greater or less extent during the 

 process just mentioned. It crystallises in small thin plates, and is 

 very similar, if not identical, with orcellic acid. 



Picroerythrin (C^H^O,,,?) is, as before indicated, a product of the 

 action of boiling water on erythric acid. On concentrating the solution 

 it if deposited in yellowish crystals, which may be obtained colourless 

 l>y re-solution in boiling water and treating with animal charcoal. 



Picroerythrin is very soluble in hot water, sparingly so in cold. II 

 has a very bitter taste, is not altered by prolonged boiling with water 

 does not etherify alcohol, readily dissolves in the fixed alkalis, and by 

 heat gives a sublimate of orcin. Its solution in ammonia rapidly 

 becomes red on exposure to the air. Boiled with baryta, or lime-water 

 picroerythrin is converted into orcin, erythro-mannite, a ^carbonate o: 

 the base, being at the same time formed. 



Picroerythrin. 



Orcin. 



Erythro. 

 mannite. 



(pteudo-orcin , 



Er>/thro-maanile (C^H^O,, -f An. ?), , 



may be obtained directly from the RucctHa by boiling for several hours 

 in lime-water, filtering, removing the lime by a current of carboni 

 acid, and concentrating the liquid to a syrupy consistence. From thv 

 cold gummy man orcin is extracted by alcohol or ether, and the 



erythro-mannite obtained pure by re-crystallisation from boiling 

 alcohol. 



Erythro-mannite is very soluble in water, the solution yielding mi 

 evaporation very fine pyramidal crystals. It has a sweet taste, but is 

 not fermentable. It is neutral to test-paper. 



The name erythro-mannite was given to this compound by Stenhouse 



m account of its properties being very analogous to those possessed by 



iiannite. [MANNITE.] Its homology with mannite is further con- 



rtncd by its yielding under similar circumstances a body very like 



nitro-mannite. 



Xitro-crt/l&ro-numiiile (C^H^NO,)^,,?) is obtained by dissolving 

 erythro-mannite in fuming nitric acid, kept perfectly cold. On adding 

 rather more than an equal bulk of strong sulphuric acid, and setting 

 aside the mixture for a short time, a large quantity of minute crystals 

 are formed ; these may be separated from the mother liquor by draining 

 n a funnel plugged with asbestos, and washing with water. I'n.ni 

 olution in alcohol the compound is obtained in beautiful crystals 

 resembling benzoic acid. 



Nitro-erythro-mannite fuses at 142 Fahr. ; at a higher tempo 

 t burns with slight deflagration. Mixed with a little sand, and placed 

 m an anvil, it detonates violently on being struck with a hammer. 

 ts solution is quite neutral to test-paper. 



ERYTHRIN. [EBTTHBIC ACID.] 



ERYTHRO-GLUCIN. [EBTTHBIC ACID.] 



KUYTHROLEIC ACID (.'), an acid of uncertain composition, said 

 a be contained in Roccella tinctoria. 



ERYTHROLEIN. [LICHENS, COLOURING MATTERS OF.] 



ERYTHROLITMIN. [LiciiKss, COLOUKINO MATTERS or.] 



ERYTHRO-MANNITE. [ERYTHRIC ACID.] 



ERYTHROPHYLLE , the substance to which the autumn 

 ,int of some leaves is due. It is soluble in water and alcohol. 

 Alkalies colour it brown, whilst salts of lead precipitate it of a 

 Beautiful green colour. 



ERYTHROPROTIDE, a red extractive matter >f uncertain com- 

 Dosition, obtained from albuminous substances. 



ERYTHROZYME. [MADDER, COLOURING MATTERS OF.] 



ERYTRARSIN (C.H^AsjO,,), a red amorphous substance forim-d 

 when cacodyl is burnt with a supply of air insufficient for its \> 

 combustion. 



ESCAPEMENT. [HOROLOOY.] 



ESCARP, or SCARP, in fortification, is that side of the ditch 

 surrounding or in front of a work, and forming the exterior of the 

 rampart. In field-works the escarp is usually formed by cutting the 

 earth at such an inclination as will permit it to support itself, which 

 may be at 45 degrees with the horizon, or more, according to the tena- 

 city of the soil ; and, to impede the enemy iu attempting an assault, 

 [raises or inclined palisades are frequently planted on the slope. In 

 large fortresses the escarp is the exterior surface of the revetment wall 

 which supports the rampart, and it is frequently formed at such an 

 inclination that the base of the slope is to its height as 1 to 6 ; that is, 

 it has a slope of J. But engineers at present recommend that the 

 exterior surfaces of both the escarp and counterscarp revetments be 

 made vertical, in order to lessen the action of the weather upon the 

 brick-work, and to prevent the formation of vegetation on the disin- 

 tegrated brick-work and the accumulated dirt iu the joints. [REVET- 

 MENT.] 



ESCARPMENT, a precipitous side of any hill or rock. In military 

 operations ground is frequently scarped, as it is called, or cut away 

 nearly vertically about a position, in order to present an obstacle to an 

 enemy. Part of the rock of Gibraltar has been rendered inaccessible 

 in this manner ; and in the execution of the entrenchments about 

 Lisbon, in 1810, the British troops formed an escarpment from 15 to 

 20 feet high, and about two miles long, on the brow of a ridge of 

 heights extending from Alhandra to the valley of Calandrix, in order 

 to secure the line against an attack at that part. A similar work was 

 executed along a ridge of hills between Mafra and the mouth of the 

 S. Lorenzo. 



ESCHAROTICS (laxapwMa., from iaxap&v, to form a crust, or 

 scab) are agents applied to the surface of the body, which destroy the 

 vitality of the part which they touch, and produce an eschar. This 

 effect they occasion either by combining chemically with the animal 

 matter, or by destroying the old affinities, and causing the elements of 

 the part to enter into new combinations. Their action is more 

 energetic in proportion to the degree of vitality of the part to trhipb 

 they are applied. They are classed under two heads, the j>" ! 

 cauterants, and the actual cautery : the former are chiefly ch< 

 agents, and form new compounds with the elements of the part with 

 which they come in contact; but some merely cause irritation and 

 augmented absorption, and arc distingnislii'd n Tin' actual 



cauterants are substances of an elevated temperature, which deoomr 

 pose the part which they touch, and completely destroy its 

 organisation. 



The chief potential cauterants are strong mineral acids, such g 

 sulphuric or nitric, pure alkalies, and some metallic salts, especially 

 nitrate of silver, or lunar caustic. These aroused either in j 

 counter-irritation, or to remove fungus or morbid growths. Lunar 

 caustic seems to possess peculiar properties, and is unquestionably the 

 most powerful direct antiphlogistic agent known. If applied in the 





