M 



EUPION. 



EVAPORATION. 



nostrils or eyes occasions violent sneezing and lachrymation, or even 

 more serious affections of the eyes, so that it is necessary for those 

 who grind this drug to protect the face by masks. Delirium and 

 stupor approaching to apoplexy have followed the inhalations of the 

 dust. When swallowed, it causes, in small doses, vomiting and purg- 

 ing ; in larger doses it produces inflammation of the stomach, and 

 sometimes proves fatal. It is now little used, even as an external 

 application to produce vesication or ulceration, except by veterinary 

 surgeons, and even by them cautiously. It is sometimes used as an 

 errhine, largely diluted with starch, and enters into the composition 

 of some cephalic and eye-snuffs ; but it is apt to be violent in its 

 effects. In case of poisoning by it, demulcent or oily fluids should 

 be given, and venesection employed if much inflammation ensue. 



EUTIOX, a liquid obtained by Reschenbach from vegetable tar, 

 especially that from beech-wood. The process for procuring it is 

 operose and complicated. Its properties are that it is very limpid, 

 colourless, inodorous, and tasteless; it boils at about 117 Fahr., and 

 distils unchanged ; it remains fluid at 4*. It is insoluble in water, but 

 dissolves in alcohol, oil of almonds and of Olives, oil of turpentine, 

 naphtha, 4c. ; it dissolves chlorine and bromine; which are evolved 

 when it is heated, and it also takes up camphor, stearin, and naph- 

 thalin, at common temperatures, but when heated, in larger quantity ; 

 with iodine it forms a blue solution. It dissolves phosphorus, sulphur, 

 and selenium when heated, but the greater portion is deposited on 

 cooling. Caoutchouc swells in it, and when heated dissolves. It is 

 not altered either by exposure to ah- or by acids or alkalies. It pro- 

 bably consists chiefly of hydride of amyl, or a mixture of the hydrides 

 of the ethylic series of radicals. 



i:r\ANTHICACID(C.,H 1 ,0 11 ,HO). PurreicAcid. There is a yellow 

 or brownish matter met with in commerce under the name of purrfe, or 

 Indian yillotc. It is imported into Europe from the East Indies, but 

 its origin is involved in obscurity ; by some it is supposed to be a 

 deposit which forms hi the urine of the camel, the elephant, or the 

 buffalo ; by others it is believed to be an intestinal concretion of some 

 animal. This material, whatever its origin, consists principally of the 

 magnesia salt of a peculiar acid, to which the above name has been 

 given. This acid is extracted by washing the Indian yellow with 

 boiling water, and then dissolving it in boiling dilute hydrochloric 

 acid. On cooling, this solution deposits pale yellow crystals of euxan- 

 thic acid. 



Euxanthic acid is very slightly soluble in boiling water, but very 

 soluble in boiling alcohol. Cautiously heated in a narrow tube, 

 euxanthic acid decomposes and forms a yellow sublimate, consisting of 

 ruxanthonr, or purrenone : 



C t H,,0,, = C, H lt O,, + 2CO, + 6HO 



Kuianthic acid. 



Euxonthone. 



With the exception of the salts of the alkalies, the euxanthates are 

 mostly insoluble in water. 



Treated with chlorine, bromine, nitric acid, or sulphuric acid, it 

 yields substitution products, of which the following are the names and 

 formula of the principal : 



Bichloreuxanthlc acid 

 Blbromcaxanlhle add 

 Nitreoxanthic add . 

 Uamathionic acid 



C. t H 14 Br,0, t 

 C 4i H,,(!TO.)0, t 

 C,iH, .0,48,0. t 



Kuxauthoiie yields similar substitution products : 



Tricblorcuxanthone 

 Tribromeu xanlhonc 

 Porphvric acid 

 Oxyporphjric add 



C..H,C1,0. 

 C..H,Br,0 lt 

 C,.H.(NO,),0.t 

 Unknown. 



KPXANTHONE. [EUXAKTHIC ACID.] 

 EVANGELIST is the Greek appellation EuanydisUi 

 from tti and SyyfAoj), which signified a messenger of any good news, ae 

 in Isaiah xli. 27, of the Septuagint version. In the first ages of 

 Christianity it was a general name of all those who, either by preaching 

 or writing, announced the " glad tidings " of the Christian revelation. 

 The learned Hooker, in his ' Ecclesiastical Polity,' b. v. 78, says that 

 " Evangelist* were presbyters whom the Apostles sent forth and used 

 as agents in ecclesiastical affairs." They were similar to the class of 

 ministers who in modern times are known as itinerant preachers. The 

 deacon (subordinate minister) Philip is called an evangelist (Acts xxi. 8 ; 

 we Grotius on the passage); so Ananias, Apollos, Timothy, and 

 several others. St. Paul, in his epistle to the Ephesians (iv. 11), places 

 evangelists in the third rank of ecclesiastical officers ; thus, apostles, 

 prophets, evangelists, pastors, teachers. Mosheim says the name was 

 applied to all those, in the infancy of the Church, who had received 

 the gift of tongues. The use of the term is now confined to the four 

 writem to whom the canonical gospels are attributed, Matthew, Mark, 

 Luke, and John, and the gospels themselves are not unfrequeutly, 

 though incorrectly, called the Evangelists. St. Jerome states that the 

 symbols of the four evangelists are a man, a lion, a calf, and an ox ; but 

 St. Augustine declares them to be a lion, a man, an ox, and an eagle. 

 (Ezekiel, i. 5-10; Rev. ir. 7.) Dr. Campbell, in his 'Dissertation on 



the Gospels' (vol. i., p. 126, &c.), gives a variety of learned and critical 

 remarks on the word tvajytUfatt, as the translation of the Hebrew 



2, bashar, ' laeta annunciare,' ' to announce good tidings.' (See 

 the word in Rose's ed. of Parkhurst's ' Gk. Lex. of the N. T.') 



EVAPORATION is the transformation of liquid, and in some 

 cases of solid substances into a gaseous state by the action of heat. 

 According to circumstances the effect may take place slowly and 

 without any apparent movement of the surface of the liquid from 

 which the vapour rises, or it may take place rapidly, and be accom- 

 panied by an ebullition. In the latter case, however, the process is 

 termed vaporisation. [BOILING OF FLUIDS ; EBULLITION]. In the pro- 

 cess of evaporation, electricity has some share, as will be noticed 

 further on. 



If a liquid be placed in an open vessel, it will be found gradually to 

 diminish in quantity by a sensible or insensible evaporation, and it 

 will at length disappear : the quantity of vapour proceeding from the 

 same liquid in a given time is evidently proportional to the area of the 

 exposed surface ; but, with equal temperatures, the escape of vapour 

 from different liquids will be fouud to take place with different 

 degrees of rapidity. An evaporation of the waters at the surface of the 

 earth is going on at all times, and over the surface of an ocean the 

 aqueous vapour held in the atmosphere amounts to an enormous 

 quantity : much of this vapour is precipitated to the earth in the form 

 of dew, rain, Ac., but it is probable that the atmosphere, at any place, 

 is never entirely free from it. 



The whole quantity of vapour which rises from a liquid having a 

 given surface appears to depend upon the temperature of the liquid ; 

 but, in a given time and in the open air, it is influenced by the state 

 of the atmosphere with respect to dryness or moisture : in dry 

 weather, even in winter time, the evaporation is more considerable 

 than in damp weather, but it is greatest when the atmosphere is both 

 dry and warm. At equal temperatures, in a close vessel, the evapora- 

 tion is the same whether the vessel containing the liquid contain also 

 air or have the air exhausted from it; but in the latter case the 

 quantity of vapour which a given degree of heat is capable of raising 

 occupies the upper part of the vessel immediately, whereas in the 

 former a certain time elapses before that quantity is disengaged. 



In order to obtain a knowledge of the quantity of water evaporated 

 in the open air, in a given time, the atmosphere being calm, Dr. 

 Dalton suspended some in a cylindrical vessel of tin from one end of 

 the beam of a balance, and raised it successively to different degrees of 

 temperature by heat : he weighed the water before and after each 

 experiment, during the continuance of which the temperature was 

 constant ; and the difference divided by the number of minutes gave, 

 for that temperature, the weight of the water evaporated in one 

 minute from the exposed surface. At the boiling-point (212 Fahr.) 

 the evaporation of water from one square inch of surface was found 

 to be equal to 4'244 grains per minute, and at a temperature expressed 

 by 138 one grain per minute : between these limits the quantities of 

 the evaporation, per square inch, in grains, are nearly proportional to 

 the heights, in inches, of the columns of mercury, whose weights are 

 equivalenttothe elastic forces of the vapour at the different temperatures. 



In these experiments no allowance was made for the effects 

 depending on vapour previously existing in the atmosphere, these 

 effects being very small compared with the elastic force of the vapour 

 rising from the water at such temperatures. But Dr. Dalton, 

 taking / to represent the elastic force of vapour in the atmosphere 

 when at the point of saturation, and f to be the elastic force of the 

 vapour in the actual state of the atmosphere, the temperature of the 

 air in both cases being that which is indicated by the thermometer at 

 the time of the experiment, found that the quantity of evaporation 

 from a square inch of surface, at such temperature, was proportional 

 iof-f, aud might be expressed by 4 Jii_* (/-/'). ('Manchester Memoirs/ 

 vol. 5.) The evaporation from ice has been determined by experiment 

 both by Dalton and Gay-Lussac, and was found to be equal in quantity 

 to that which, by computation, would take place from water at the 

 same temperature. 



To Dr. Dalton we owe also the discovery, admitting however that 

 the aqueous vapour in the atmosphere has no influence on evaporation, 

 that the quantity of vapour raised from a given surface of any liquid, 

 at a given temperature, is directly proportional to the elastic force of 

 the vapour at that temperature ; therefore, if the clastic forces of the 

 vapours from different liquids were correctly ascertained, a near ap- 

 proximation, at least, might be made to the amount of evaporation 

 from those liquids. At a temperature equal to 212 (Fahr.) the 

 elastic force of the vapour from water is equivalent to the weight of a 

 column of mercury 30 inches high ; the elastic force of the vapour of 

 one kind of alcohol, to the weight of t a column 68 inches high ; and 

 that of the vapour of one kind of ether, to the weight of a column 219 

 inches high. 



It is stated by Mr. Faraday that, at temperatures above 60 or 80 

 Fahr., there is a small evaporation from mercury; at lower tem- 

 peratures he could detect none; and he concludes that, below the 

 temperatures just mentioned, the gravity of the particles of mercurial 

 vapour exceeds their elastic force. In this material, as well as in all 

 liquids which boil at high temperatures, the elastic force of the vapour 

 is very small. Sulphuric acid, for example, boils at 640 Fahr., but it 

 emits no vapour at ordinary temperatures. Most solid substances 



