4*1 



CACODYL. 



CADENCK. 



, that when poured Into oxygen, chlorine, or the air, it 



take* fire; it boils at S38* ; when cooled to 81* it crystallises in Urge 

 transparent square prism*. It is heavier than water, and being nearly 

 insoluble in it, sinks when added to it. Alcohol and ether dissolve it 



mil* U C.H.A* = Kd. 



Ofide of Ckc+dyl. Equal part* of arsenious acid and acetate of 

 potash are to be accurately mixed and put into a gU*s or iron retort, to 

 which a cooled nearer is adapted, with an apparatus to carry off the 

 moondeasible gaseous product, which u chiefly carbonic aeid ami 

 hydride of methyl. When the heat ha* been long continued, some 

 metallic anenic and two liquid* are found in the receiver : the lighter 

 1 1 insists mostly of water, with acetic acid and acetone ; and the heavier 

 it impure oxide ot cacodyl, or alcarrin, formerly called the liquor of 

 < < 



The product u obtained in a pure state by repeated washing with 

 water free from air, and redistillation from hydrate of potash in > 

 retort containing hydrogen gu; this operation, on account of the 

 poisonous nature of alcanin, must be conducted with great care and 

 special arrangements made for conveying away the fumes from the 

 neighbourhood of the experimenter. 



ThV properties of thia substance are : It is a colourless liquid ; 

 its density u 1*462 ; its smell is extremely disagreeable, and the vapour 

 affect* the eyea and nose. Water dissolve* little of it, but alcohol 

 takes it up readily; it boils at about 248, and solidifies, becoming :\ 

 white crystalline man, at 9*. By exposure to the air a dense white 

 smoke is emitted, the alcanin becomes hot, and afterwards burns 

 spontaneously with a pale flame, producing arsenious acid, carbonic 

 acid, and water. It is composed of 4 equivalents of carbon =24, 6 

 equivalents of hydrogen = 6, 1 equivalent of arsenic =75, 1 equivalent 

 of oxygen = 8. Its formula is C.H. AsO - - KdO. 



duaride of Oacodyl. Mix a dilute alcoholic solution of oxide of 

 cacodyl with one of corrosive sublimate, avoiding on excess of the 

 latter; by their mutual action a colourless inodorous crystalline pre- 

 cipitate is obtained (C.HjAsO, UgCl) ; and when this is distilled with 

 hydrochloric acid, there are formed water, chloride of mercury, and 

 chloride of cacodyl, the latter coming over ; this is subjected to the 

 action of lime and chloride of calcium, and then distilled in a retort 

 containing carbonic acid gas. The chloride of cacodyl thus produced is 

 a colourless liquid ; it* odour is more disagreeable and its vapour more 

 poisonous than that of the oxide of cacodyl ; it d<KU not fume when 

 exposed to the air, but its vapour, which is colourless, is spontaneously 

 inflammable in it. It is heavier than and insoluble in water ; alcohol 

 combines with it readily, but ether does not; its boiling-point is a 

 little above 212. Its formula is K< 'I. 



Indide ,,f Carodyl (C.H.AsBr), and Bromide of Ciieodyl (C.H.AsI). 

 may be formed by treating the above hydrargyro-oxyohloridc of cacodyl 

 with hydriodic, or with hydrobromic acid. 



Cyanide nf Carodyl (C.HJU, M', ^K.l('y) may be obtained by 

 distilling oxide of cacodyl with hydrocyanie aeii], or a strong solution 

 of cyanide of mercury. The product LTjM.ilIi.-'es in brilliant prisms. 

 Fusing point 91, boiling point 284. Vapour density 4'03. This 

 compound U even more deadly poisonous than the other compounds of 

 cacodyl. A single gram diffused in vapour through the atmosphere of 

 an ordinary apartment cause* numbness of the hands and feet, 

 giddiness, a buzzing noise in the ears and sometimes fainting; but 

 usually these symptoms arc of short duration after the poisoned air has 

 been removed. 



Smlpkid,. ,,f l', lf *lyl (C.H JU,S = KdS) is best obtained by distilling 

 a mixture of sulphide of barium and chloride of cacodyl. It is a 

 colourless transparent liquid, of an exceeding penetrating fetid odour. 

 Its liling ]mint i 212. It does not solidify at a temperature of 40*, 

 Vapour density 772. It is insoluble in water, but miscible in all 

 proportions with alcohol and etlier. 



>W/<Ann->/yi>- A>-itt (C.II.AsS,), or tersulphide of cacodyl. is 

 obtained in conibinati< >n by precipitating metallic salts with sulpho- 

 cacodylato of cacodyl, or l.imilphidc of cacodyl, a comjiouud obtained 

 by acting upon cacodylic acid with Hulplmretteil hydrogen. 



I flic Acid (C.H r AsO, = KdO 1 ). AI.-. ;/ ... ' \V1,, cacodyl or iU 

 oxide U left nnilvr water to the slow action ot tin- air, iliey oxidise and 

 become cacodylic acid ; or it may be prewired by adding oxide of mer- 

 cury to oxide of cacodyl, covered with a layer of water, and artificially 

 cooled until the mixture loses all odour ; any cacodylato of mercury \\ hicli 

 may have been formed is to be decomposed by the cautious addition of 

 more oxide of oacodyl ; by evaporation to dryncns and solution in alco- 

 hol crystal* of cacodylic acid are <,l,t >in.-.l, which have the following 

 properties : They are colourless, brittle, brilliant, prismatic crystals ; 

 perminent In a dry atmosphere, but deliquescent in a moist one. 

 Cacodylic acid is iiw.lul.lc in ether, but dissolved by alcohol, and the 

 solution has an acid reaction ; it yield* by combination with the 

 alkalies, and evaporation, a gummy mass ; it forms crystalline com- 

 pounds with the oxides of silver, mercury, 4c. 



From experiment* tried on snimali, it would secui, that cacodylic 

 acid possesses little or no poisonous quality. This is somewhat 

 remarkable, especially when we bear in mind that it contains more 

 than half it* weight of anenic. 



Cacodyl combines with various other bodies, yielding compound* 

 which have been particularly described by Bunscn, sod of which an 

 account may be seen in a series of papen published by that eminent 



chemist in Liebig's 'Aimalcu,' voli. zzzvii. xlii. xlvi. 

 METALLIC BODIES.] 



CACODYLATES. [CACODTL.] 



CACODYLIC ACID. [CACODTL.] 



CACOPLATYL (C.H.PtAs). This body may be represented a* 

 cacodyl in which two equivalents of hydrogen are replaced by one of 

 diatomic platinum. When a mixture of solutions of el.!..- 

 oacodyl and bichloride of platinum are heated and allowed to cool, 

 crystals of chloride of cacuplatyl separate out, the reaction is expressed 

 in the following equation : 



CVH.As, a + PtCl, JHC1 + C 4 (H.Pt) As, Cl 

 Chloride of cacodyl. Chloride of caooplatvU 



Chloride ofCacojJatyl crystallises in beautiful needles. It is inodorous, 

 and has a nauseous arsenical taste, is soluble in hot water and hot 

 alcohol, and when heated darkens in colour, takes fire, and smoulders 

 away, giving off arsenical fumes and leaving a fusible residue of 

 arsenide of platinum. Sulphuric acid colours it yellow. It is very 

 soluble in ammonia, and the solution yields on evaporation a crystal- 

 line body insoluble in a! 



The Bromide of Cacn/Jali/l (C.H, PtAs, Br.) and the iuditU </ 

 jil'iti/l ((',11, PtAs, I) ore obtained by decomposing chloride of caco- 

 platyl with bromide or iodide of potassium. They are both beautifully 

 crystalline, soluble in hot water, and have a disagreeable arsenical 

 taste. They each contain two equivalents of water of crystallisation. 



The Sulphate of Cacoplatyl is obtained by boiling chloride of cacuplatyl 

 with a solution of sulphate of silver. It has the fonu of white 

 crystalline grains, is very stable, without odour, and of a bitter and 

 astringent taste. [ORGANO-METALUC BODIES.] 



CACOTHELIXK. [Nfx VUMICA, ALKALOIDS OF.] 



CACTI X. When the flowers of the Cactiu ijxciona are extracted 

 with alcohol they yield a carmine red colour, to which the name of 

 cactin has been given. Its composition and properties arc not known. 



CADENCE, in Music (cadenza, Ital., cadi -. . l-'i . . 

 In fall), the close of a musical passage or phrase, or the resolution of a 

 dissonant chord into a consonant one. 



Cadencft, which are in some degree analogous to punctuation in 

 grammar, ore resting places for the mind, serving to divide a composi- 

 tion into several parts, or to separate the different mcmbei 

 niu-lcal sentence. They are either perfect or imperfect. The perfect 

 cadence is composed of the chord of the dominant, foil. .wot by tliat of 

 the tonic ; likewise of the chord of the dominant seventh, succeeded 

 by that of the tonic. 



EXAMPLES. 



I 



"I T 



The first and second inversions of the dominant seventh, followed 

 by the chord of the tonic, also form perfect cadences, but are rarely 

 used as final cadences. 





EBr 







The imperfect cadence consists of til* chord of the ton!,-, followed by 

 that of the dominant, but in never met with as a final close, except in 

 some very few old ecclesiastical compositions. 





I 



Albrcchteberger gives the subjoined formula! of thin cadence. 

 No. 1. No. 2. 



But in No. 2, the introduction of the F sharp changes the key 



