10 LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. BY FREDERICK PEACOCK LEACII. THE reaction between pinene nitrosochloride and potassium cyana te does not, as one might expect, lead to the production of a carbimide by the replacement of the chlorine by the -N:C:O group, but instead gives rise to a somewhat complex ring compound having the empirical formula CI2Hl70,N,. Interaction bet ween the nitrosochloride and potassium cyanate takes place quite readily in alcoholic solution a t 45-50', two molecular proportions of the cyanate reacting with one of the aitrosocliloride. The constitution of the new compound is probably best expressed by the formula or one of the tautomeric forms, This conclusion has been reached by considering the following ex- perimental evidence : (I) The substance behaves like an imide, having a feebly acidic character, dissolving i n caustic alkalis, and giving alkali salts like succinirnide or phthalimide. (2) When reduced by dilute acetic acid and zinc dust it loses carbon dioxide and ammonia, owing to liberation of cyanic acid, and a very stable peudocarbamide is formed : c H <?=No-co>NH + 2H2 = l2 CMe*NH*CO C 7 H l 2 < ~ ~ - - ~ ~ > C O + NH, + CO,.(3) Warm concentrated sulphuric acid hydrolyses the imide and the ring undergoes disruption ; carbon dioxide and ammonia are liberated and pinene nitrolamine is formed :LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. 11 The mechanism by which the seven-membered ring is produced from the nitrosochloride has not been fully explained, but there seems no doubt that the condensation is brought about in some way by free cyanic acid, which can be rscognised in the liquid by means of the cobalt acetate test.The most probable explanation depends on the resolution of the bimolecular nitrosochloride into the unimolecular (oximino) form, and replacement of the chlorine by the group -N:C:O ; interaction of the free cyanic acid with the oximino-group would give a carbamic derivative of the oxime, which then undergoes rearrangement, forming the complex imide : This new compound is exceedingly stable towards oxidising agents. Whilst pinene and its compounds are, generally speaking, readily oxidiaed or altogether destroyed by nitric acid, the new compound can be boiled with concentrated nitric acid (sp. gr. 1*42), and on dilution with water crystallises in needles.I n a similar manner, when dis- solved in cold alkali and treated with alkaline hypobromite, the unchanged substance is precipitated from the solution. Towards reducing agents the substance is very sensitive, and as already pointed out i t gives rise by the action of zinc and dilute acetic acid to a pseudocarbamide from which the corresponding nitroso-$- carbamicie and peudosemicarbazide have been obtained. These sub- stances have a close relationship to the corresponding derivatives of camphor, recently isolated and examined by Porster and Fierz (Trims., 1905,87, 110 and 722) : Piny1 - I/I - carbamid e . Caruphoryl-$-carbamide. The pseudocarbamide from pinene possesses a very stable ring structure, for it sublimes unchanged at 224' and is scarcely acted on by hot 30 per cent.caustic potash or dilute acids. The camphoryl compound possesses a labile hydrogen atom, owing to which the ring can be opened by dilute acids, giving the carbamide of aminocamphor, from which alkalis regenerate the peudocarbamide. The action of nitrous acid on the pseudocarbamide from pinene12 LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. gives rise to a nitroso-derivative, crystallising in beautiful yellow plates with a delicat.,e pink lustre. The stable nature of the ring in the pseudocarbamide makes it difficult to determine the position taken up by the nitroso-group : for the present, therefore, it is not possible to decide between the f ormuls CH---NH>Co C H 'I l2 <$!H*N(No) CMe--NH and C 7 H 1 2 < ~ ~ e .~ ~ ~ ~ ) ' A similar uncertainty exists in the case of the pseudosemicarbazide. Although remaining unchanged in the dark the nitroso-$-carbamide when exposed to light undergoes a series of interesting changes : in sunlight the colour changes in the course of a few minutes from the characteristic yellow with pink reflex to a bright green, whilst after some hours the green begins to fade and is followed by a dull yellow colour, further exposure causing no alteration ; besides change of colour the crystals become opaque and '' pitted " on the surface owing to escape of gas. This change, which is accompanied by decrease of fusibility, has been proved to be due to the elimination of the nitroso- group, with the regeneration of the pseudocarbamide.The readiness with which the nitroso-group is detached appears from the fact, that if a few crystals of the nitroso-compound are placed in a test-tube with a little potassium iodide and starch solution, and one drop of dilute sulphuric acid is added, the blue colour due to the liberation of iodine makes its appearance in the course of a few minutes. Cazeneuve (Compt. rend., 1889, 109, 185) noticed somewhat similar changes of colour in the case of nitrosocamphor (compare Claisen and Manasse, Annalen, 1893, 2'74, 72) : The introduction of the nitroso-group into the pseudoaarbamide renders the product soluble in dilute caustic soda, from which the sodium salt is precipitated on further addition of cold concentrated caustic soda ; if, however, the solution is heated, decomposition takes place, gas being evolved and an oil having a camphoraceous odour being produced.The reduction of the nitroso-t)-carbamide gives rise to a crystalline pseudosemicarbazide : The products of the reaction are still under investigation. The tendency, however, for the nitroso-group to become eliminated as ammonia is very considerable, and unless the conditions given for the preparation of the pseudosemicarbazide are adhered to, a product is obtained which is very difficult to purify.LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. 13 The new base res'kmbles semicarbazide itself in combining with great readiness with aldehydes and ketones to form the corresponding pseudo- semicarbazones ; with acetone, however, no condensation product has been obtained.The quinone-$-semicarbazone crystallises in bright yellow needles and contains one molecule of water of crystallisation, which it loses a t 100'; products obtained by condensation of the pseudosemicarbazide with aldehydes, however, are free from solvent. The hydrochloride of the base when heated with nitrous acid at 0' regenerates the pseudocarbamide, and if excess of hydrochloric acid is present, the nitroso-$-carbamide is obtained, owing to the action of the nitrous acid on the pseudocarbamide. The reaction is most probably expressed as follows : (I) C 7 H , , < ~ ~ ~ ~ ~ ~ > C 0 + HNO, = 7H1 2<gEz!E >CO + N20 + H,O. (11) C , H , , < ~ ~ ~ ~ ~ > C O + HNO, = This observation is in agreement with that of Emil Fischer (Annalen, 1877, 180, 158), who found that when sodium nitrite acted on phenylmethylhydrazine in dilute sulphuric acid the nitroso- compound of pheoylmethplamine was obtained, C,H5(CH,)N*NH, + 2HN02 = C,H,(CH,)N*NO + 2H,O + N20, this action doubtless also takes place in two stages.The behaviour of the camphoryl-$-semicarbazide (Forster and Fierz, Trans., 1905, 87, 826) resembles that of the pinene compound, if the reaction is carried out in acetic acid solution, when the pseudo- carbamide is obtained, but excess of sodium nitroso-$-carbamide ; it differs, however, in nitrate of the camphoryl-q-semicarbazide is the ring undergoes disruption, with the azoimide. The compounds of pinene described in inactive. nitrite does not yield the the fact that when the treated with nitrous acid formation of camphoryl this paper are optically EX P E R I MENTAL. The most satisfactory method of obtaining this compound is to treat the nitrosochloride of pinene in quantities of 20 grams at a time,14 LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE.larger quantities cause the formation of more resinous matter. Twenty grams of freshly prepared pinene nitrosochloride were ground to a fine powder with 18 grams of potassium cyanate and the mixture added to 150 C.C. of rectified spirit, the whole being shaken from time t o time. I n the cold, the reaction proceeds very slowly, but on allowing to stand at 45-50' the nitrosochloride gradually disappeared and potassium chloride was precipitated along with a quantity of small, hard crystals of the imide, which is only very sparingly soluble in cold alcohol ; the solution developed a pale yellow colour, owing to the formation of a certain amount of a yellow, resinous oil, and in about four days the whole of the nitrosochloride had disappeared; sufficient water was added to dissolve the potassium chloride and on filtering there was left an almost pure residue of the new compound, which after two recrystallisations from hot alcohol was quite pure.On pouring the alcoholic solution into a large volume of water a yellowish- white, bulky solid, mixed with small quantities of oily matter and re- generated pinene,wasprecipitated, from which after filtering, drying, and extracting, with light petroleum, the crude imide was obtained. The light petroleum, on evaporation, left a brown, resinous oil having an odour of turpentine, and after some time crystals were deposited, which when recrystallised twice from alcohol melted at 131" and gave no de- pression when mixed with nitrosopinene.From 100 grams of pinene nitrosochloride, 70 grams of the crude imide were obtained. The imide dissolves moderately in hot alcohol, crystallising in rosettes of hard prisms having the appearance of truncated octahedra, and after two recrystallisations the substance is quite colourless and melts at 238-240" with some previous discoloration. In cold solvents the new compound is only very sparingly soluble, but crystsllises from hot, dilute acetic acid in prismatic needles, from hot methyl alcohol in small prisms, and from hot water, in which it is only slightly soluble, in needles ; in basic solvents such as aniline or pyridine, the h i d e is readily soluble : 0,1139 gave 0.2388 CO, and 0.0704 H20.C=57*18; H=6*96. 0.1326 ,, 0.2788 CO, ,, 0,0843 H20. C=57.34; H=7*06. 0.1226 ,, C12H170,N, requires C = 57-37 ; H = 6.77 ; N = 16.73 per cent. 18.2 C.C. moist nitrogen at 19" and 766 mm. N = 17.19, C,,H,,O,N, ,, C = 57.14 ; H= 7.14 ; N = 16.66 ,, ,, When boiled with dilute hydrochloric or sulphuric acid the substance is not changed and the solution when made alkaline does not reduce Fehling's solution ; prolonged boiling, however, with con- centrated hydrochloric acid decomposes it, giving oily products, and the solution yields a red precipitate of cuprous oxide on addition of Fehling's solution and caustic alkali.LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE.15 Action of Nitric Acid.-The imide dissolves readily in cold concentrated nitric acid (sp. gr. 1-42), forming a colourless liquid with but slight development of heat ; the liquid on boiling becomes yellow and a reaction appears to take place with evolution of red fumes: addition of water., however, precipitates the unchanged imide in fine needles, This behaviour is remarkable in a pinene derivative and supports the view that the substance is a ureide or ring compound of a very stable nature. Potassium Salt.-2.5 grams of the imide were ground to a fine powder and mixed with 15 C.C. of cold alcohol, 0.6 -gram of caustic potash dissolved in the smallest quantity of water was then added ; the imide dissolved and almost immediately a solid, white mass of the potassium salt was precipitated, which, after filtering and washing with a little absolute alcohol, was dissolved in absolute alcohol and re- precipitated by addition of dry ether : 0.5855 gave 0.1737 K,SO,.K = 13.31. C,,H,,O,N,K requires K = 13-49 per cent. The potassium salt is extremely soluble in cold water, and when carbon dioxide is passed into the solution the imide is precipitated as a very bulky mass of fine needles; exposure t o air causes the salt to decompose slowly owing to the action of moisture and carbon dioxide. It dissolves readily in warm alcohol, from which it crystallises in large, rhombic prisms, but is insoluble in dry ether. Sodium Salt.-This is prepared in a similar manner to the potassium salt ; it differs, however, in being more soluble in cold alcohol.Addition of dry ether precipitates it in white and somewhat opaque needles. ActioPa of Alkali.-The imide dissolves very readily in dilute aqueous caustic alkalis, being reprecipitated by addition of dilute acids ; if, however, the substance is boiled with 30 per cent. aqueous caustic potash, the liquid acquires a red colour and evolves ammonia. During the course of the reaction a crystalline deposit appeared in the con- denser and proved to be nitrosopinene (m. p. 131') ; after the evolution of ammonia had ceased the liquid was diluted with water and acidified with hydrochloric acid, when evolution of carbon dioxide and the separation of crystalline matter took place ; the latter after recrystal- lisation yielded a considerable quantity of nitrosopinene : CNOH CNe*NH,' Conversion into Pinene Nitrolamine, C,H,,< I Five grams of the imicle were added gradually to 20 C.C.of concen- trated sulphuric acid, when considerable development of heat occurred,16 LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. and a colourless solution was formed; on heating to 85O, effervescence took place with evolution of carbon dioxide and formation of ammonium sulphate, the liquid became pale yellow and finally red. After tbe evolution of gas had ceased, the liquid was cooled and poured on to crushed ice, yielding a. clear solut.ion. Addition of aqueous caustic soda gave a crystalline precipitate which immediately dissolved in excess of the alkali, and the colour of the solution changed from red to yellow; carbon dioxide changed the colour to red again and pro- cipitated a crystalline deposit of fine needles, which, when filtered and recrystallised from alcohol, softened a t 118' and melted a t 1 2 3 O with evolution of gas.Further recrystallisation did not alter the melting point, and the substance remelted at 129-131", behaving exactly like pinene nitrolamine : 0.1800 gave 24.0 C.C. moist nitrogen a t 20' and 772 mm. N = 15.50. C,,H,,ON, requires N = 15.38 per cent. When mixed with pinene nitrolamine, obtained by the action of ammonia on pinene nitrosochloride (see preceding paper, page 4), no depression of the melting point took place. It forms a hydro- chloride identical with that of pinene nitrolamine, and therefore its identity is established : I n order to ascertain whether free nitrogen was eliminated during the reaction between the sulphuric acid and imide, a weighed quantity of the latter was placed in a small flask attached to a carbon dioxide apparatus and a nitrometer in the usual manner, when it was found that the whole of the gas expelled on warming the flask to 100' was absorbed by the caustic potash in the nitrometer, and on adding caustic potash to the diluted sulphuric acid solution in the flask, ammonia was evolved.CH--NH l2 CMe*NH PinyZ-$-carbamide, C H < I >GO. Twenty grams of the imide were powdered and suspended in a mixture of 75 C.C. of glacial acetic acid and 40 C.C. of water, 35 grams of zinc dust were gradually added to the pasty liquid, and the mixture shaken from time to time, the temperature not being allowed to rise above 50".I n a short time the liquid became frothy, owing to the evolution of carbon dioxide, and had an odour recalling that of an isocyanate. The elimination of ammonia took place simultaneously, and was detected by addition of caustic alkali to aLEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. 17 small portion of the solution. When the liquid had become quite clear, it was heated on the water-bath for an hour, and on adding ammonia, a bulky, white precipitate of small needles, mixed with some oily matter, was obtained, which when filtered and dried gave a pale brown product with an odour of peppermint, due no doubt to the formation of small quantities of the ketone (Wallach's pinocamphone). From 100 grams of the imide, 60 grams of the crude, dry pinyl-+- carbamide were obtained, giving, after recrystallisation from hot dilute alcohol, aggregates of colourless but almost opaque prismatic needles melting at 224' without decomposition.The crystals when deposited from the solution were transparent, but after separating and drying in the desiccator became opaque, probablydue to loss of solvent of crystallisation : 0.1121 gave 0.2782 CO, and 0.0940 H,O. C = 67.67 ; H = 9-31. 0.1798 ,, C,,H,,ON, requires C = 68.04 ; H = 9.26 ; N = 14.43 per cent. The pseudocarbamide is readily soluble in hot water, methyl alcohol or acetic acid, sparingly so in chloroform or ether, whilst in light petroleum it is almost insoluble. Cold concentrated sulphuric acid dissolves the pseudocarbamide, which is reprecipitated by ammonia.When heated with 30 per cent. aqueous caustic potash no ammonia was evolved, the substance appearing quite unchanged. The very stable nature of the pseudocarbamide is further emphasised by the fact that, when heated in a dry test-tube, it sublimes and condenses in small leaflets on the sides of the tube. 22.6 C.C. moist nitrogen a t 27" and 758 mm. ..N = 14.61. Beduction, of the Imide by Glccciul Acetic Acid and Zinc. I n the first experiments on the reduction of the imide it was noticed that if glacial acetic acid and zinc dust were used, a white, crystalline, but very insoluble compound separated from the liquid, and although a certain amount of the pseudocarbamide was produced, it was largely contaminated with this insoluble substance, Thirty grams of the imide were suspended in 200 C.C.of glacial acetic acid and 40 grams of zinc dust gradually added with shaking ; after a short time an almost clear solution resulted, and the reaction was com- pleted by heating for several hours on the water-bath. Water was then added t o dissolve zinc acetate, and the liquid on being decanted from the zinc residues contained the insoluble matter in suspension ; after filtration and washing with water, a colourless, crystalline com- pound was left which was insoluble in boiling alcohol or other solvents, except hot acetic acid, from which it crystallised on cooling in small, hard prisms which did not melt below 300'. The filtered liquid when poured into water gave a further quantity VOL. XCI. C18 LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE.of the insoluble substance, and after filtration and addition of ammonia a crystalline deposit of the pseudocarbamide was obtained : 0.1282 gave 0.3000 CO, and 0.1026 H,O. 0.1418 ,, 15.7 C.C. moist nitrogen at 19' and 753 mm. N = 12.59. C,2H200,N, requires C = 64.28 ; H = 8.92 ; N = 12.50 per cent. When this substance was heated in the water-oven, acetic acid was given off, and after being dried at 100' it lost 10 per cent. of its weight; the whole of the acetic acid, however, was not evolved, because on warming a small portion of the dried substance in a test- tube the pungent and characteristic odour was noticed. This compound is insoluble in dilute acids and alkalis, but dissolves in concentrated sulphuric or nitric acid, and on dilution is precipitated unchanged.Reduction of the imide by alcoholic hydrochloric acid and zinc dust also yielded small quantities of the same insoluble com- pound, and it is hoped that further investigation will elucidate its constitution. C = 63.52 ; H = S%9; Twenty grams of the pseudocarbamide were made into a paste with water and mixed with 200 C.C. of water and 20 C.C. of concentrated hydrochloric acid, the liquid was cooled to Oo by the addition of crushed ice, and 10 grams of sodium nitrite added in small portions at rz time with stirring. The pseudocarbamide was rapidly attacked, and a pale yellow, bulky solid was precipitated; after standing for an hour the liquid was filtered, when 19 grams of a bright sulphur-yellow nitroso- compound were obtained which crystallised from alcohol in small, yellow, hexagonal plates with a distinct red lustre when viewed by reflected light : 0.1 127 gave 0.2436 CO, and 0.0798 H,O.C = 58.95 ; H = 7.86. 0.1072 ,, 17.4 C.C. moist nitrogen a t 1 7 O and 754 mm. N = lS.68. C1,H170,N3 requires C = 59.19 ; H = '7.62 ; N = 18.83 per cent. The nitroso-$-carbamide gives the Liebermann reaction in all its stages, but so far its action towards aniline has not been studied ; it is readily soluble in methyl or ethyl alcohol, from which i t crystallises in plates ; it dissolves in chloroform or acetic acid, being precipitated from the former by light petroleum in clusters of needles ; in warm benzene it is only moderately soluble, and very sparingly so in light petroleum.Action of Caustic AE?caZi.-The nitroso-$-carbamide dissolves in 10 per cent. alkali, giving a colourless solution, and on additiori of a concentrated solution of the alkali the sodium salt is precipitated in pearly leaves, which, after filtration, washing with a little alcohol, and drying on a porous plate, yield a colourless but impure substance. If,LEACH : A PSEUDO-SEMICARRAZIDE FROM PINENE. 19 however, the nitroso-compound is warmed with 25 per cent. aqueous caustic soda it partially dissolves, nncl on further warming a yellow oil appears with evolution of gas ; the liquid has a camphoraceous odour, and on cooling yields a semi-solid, crystalline mass ; addition of dilute sulphuric acid with a few drops of starch and potassium iodide solution gives an intense blue colour, showing that nitrous acid has been with- drawn from the nitroso-q-carbamide.The investigation of the pro- ducts 'of the reaction is not yet complete. Action of' Light on the Nitroso-+-curbamide. When freshly prepared the nitroso-compound is yellow with a delicate pink reflex; it was noticed, however, that if left exposed to light and air the crystals soon developed a bright green colour. Some experiments were therefore made in order to ascertain to what cause this change of colour is due. When the nitroso-+-carbamide is spread out in a thin layer on a flat-bottomed dish, covered with a clock glass, and exposed to sunlight, the colour of the crystals changes in the course of a few minutes to a bright, opalescent green and after some time to a deeper t i n t ; examined by the lens, the surface of the crystals appears quite bright and the colouring uniform, but after exposure for some hours the green tint begins to fade and the surface becomes white and opaque.The crystals lose their trans- parent character and finally, after about a week's exposure, they become dull yellow, further exposure causing no alteration. The melting point of the pure nitroso-$-carbamide is 16l0, but after exposure the crystals did not melt until 190' was reached, and then after considerable previous softening. On examination under the microscope, the crystals were no longer bright and transparent, but of a dull uniform yellow colour, the surface of the crystals appear- ing '' pitted '' as if gas had escaped and minute crystals had grown on the surface of the larger ones, whilst the angles had lost their sharp and well-defined character.The product obtained after exposure differed from the nitroso-+-carbamide in being insoluble in dilute caustic alkalis and in not giving the Liebernlann reaction ; after recrystallisation from dilute alcohol the melting point gradually rose to 2 2 2 O , and on mixing with the pinyl-+-carbamide no depression was observed. I n order to prove its identity with the latter substance, a small quantity of the recrystallised product was added to crushed ice mixed with a little dilute hydrochloric acid; addition of sodium nitrite precipitated the original nitroso-1C/-carbamide melting at 16 lo. The fact, therefore, that the nitroso-$-carbamide eliminates the nitroso-group when exposed to light is proved ; it appears probable, c 220 LEACH : A PSEUDO-SEMLCARBAZIDE FROM PINENE. however, that this change is brought about by the action of moisture, causing hydrolysis : This hypothesis was tested by placing a small quantity of the nitroso-compound in a test-tube with two or three C.C.of distilled water, and a few drops of potassium iodide and starch solution, but no colour appeared after several hours ; on repeating the experiment with the addition of one drop of dilute sulphuric acid, the blue colour appeared in a few minutes. CHON( NH,) CMe-NH Pinyl-+-semicadaxide, C7H12< I >CO. Twenty grams of the nitroso-+-carbamide were made into a paste with 20 C.C. of water, and mixed with 150 C.C. of water and sufficient crushed ice to reduce the temperature below 5 O . Twenty-five C.C.of glacial acetic acid were added, and 25 grams of zinc dust stirred in gradually, together with more ice if necessary. The yellow nitroso- compound dissolved slowly, forming a clear solution, and after half- an-hour had elapsed 10 C.C. of acetic acid were added, the re- duction being complete in about two hours. The liquid was then filtered from zinc and evaporated to 500 C.C. The acetic acid, after being partially neutralised by addition of concentrated ammonia, caused the precipitation of brown, viscid matter, and after filtration a nearly colourless liquid was obtained, from which by further addition of ammonia the pseudosemicarbazide was precipitated in a fairly pure condition. From 20 grams of the nitroso-#-carbamide, 9 grams of the pseudosemicarbazide were obtained, which crystallised from hot alcohol in colourless, small, rhombic prisms melting at 209".The specimen analysed was dried at 100' for half-an-hour : 0.1360 gave 0.3138 CO, and 0.1158 H,O. 0.1074 ,, 19.2 C.C. moist nitrogen at loo and 752 mm. N = 20.32. C,,H,,ON, requires C = 63.15 ; H = 9-09 ; N = 20.09 per cent. The pseudosemicarbazide dissolves readily in warm methyl or ethyl alcohol, chloroform, or acetic acid, and moderately in warm acetone or benzene, crystallising from the latter in transparent plates; it is sparingly soluble in ether, and insoluble in light petroleum, and crys- tallises from water in t u f t s of minute needles. Towards ammoniacal silver nitrate it acts as a powerful redncing agent, giving a black deposit of metallic silver in the cold ; with Fehling's solution, however, no action takes place, but on warming a copious precipitate of cuprous oxide is deposited, evolution of gas occurs, and an oil separates, having at first an odour of peppermint (probably pino- C = 62.92 ; H = 9.46.LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE.21 camphone) and, after the lapse of a few minutes, distinctly that of carvone. This reaction appears to be similar to that observed by Forster and Fierz (Trans., 1905, 87, 727), who found that oxidation of camphoryl-y?-semicarbazide with Pehling's solution gave rise to camphor. Ferric chloride added to a cold alcoholic solution of the JI-semi- carbazide caused a slight evolution of gas which became much more brisk on warming ; addition of water precipitated a white, crystalline substance.The pseudosemicarbazide did not give a platinichloride, for on warming the solution became dark, evolved gas, and yielded a tarry residue with an odour of turpentine; in this respect the pseudosemi- carbazide of pinene behaves like semicarbazide itself (Thiele and Stange, Annalen, 1894, 283, 21). The hydrochloride was obtained by passing dry hydrogen chloride into a solution of the pseudosemicarbazide in ether, a finely-divided, crystalline precipitate separated, and when filtered and recrystallised from absolute alcohol was deposited in thin, lustrous plates decomposing indefinitely at 250' : 0.3978 dissolved in water required 16.4 C.C. N/lO AgNO,. C1= 14.58. C,,H,,ON,Cl requires C1= 14.45 per cent.No indicator need be used in the titration because the slightest excess of silver is shown by the solution turning black, owing t o the strong reducing action of the pseudosemicarbazide. Towards hot concentrated hydrochloric acid the base is quite stable, the hydro- chloride being deposited on cooling. Copper Nitrate Double Salt.-The base, dissolved in the 1ea.st quantity of dilute nitric acid, was added to a concentrated solution of copper nitrate in absolute alcohol ; from the green solution bright blue needles were deposited, and after recrystallisation from hot water the czcpri- nitrate was obtained in tufts of blue needles decomposing about 175' : Cu = 8.79. (C1,H190N,,HN0,)2,Cu(N0,), requires Cu = 8.68 per cent. 0.1760 gave 0.0194 CuO.The PinyZ-$-semicarbazo~~es. Pinyl-$-semicarbazide combines with aldehydes and ketones with great readiness ; with acetone, however, no condensation product has been obtained. The base is dissolved in dilute acetic acid, diluted largely with water and the requisite quantity of the aldehyde or ketone, also dis- solved in dilute acetic acid, added. The liquid becomes turbid, and on gently warming the pseudosemicarbazone separates, of ten as a viscid oil, soon becoming crystalline, or directly in a crystalline condition.22 LEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. With the exception of the quinone-$-aemicarbazone, there appears to be little or no tendency to combine with the solvent such as was exhibited in the case of the corresponding camphoryl derivatives (Forster and Fierz, Trans., 1905, 87, 725); the quinone compound, however, retains one molecule of water, which is not lost in the desiccator, but on heating to 100" is completely eliminated.Benxylidene Pin~l-~-senzicarbuxolze, is precipitated by the addition of benzaldehyde to the solution of the base in dilute acetic acid. It crystallises from alcohol in rhornbic prisms which melt at 180", remelting at the same temperature. It dissolves readily i n cold chloroform, and is reprecipitated by light petroleum in colourlees, rhombic prisms ; it dissolves readily in cold acetic acid, but is much less soluble in ether and almost insoluble in light petroleum : 0.1491 gave 18.4 C.C. moist nitrogen at 18" and 770 mrn. N = 14.43. C,,H,,ON, requires N = 14-14 per cent.The benzylidene derivative is insoluble in dilute hydrochloric acid, but when heated hydrolysis takes place, giving a strong odour of benzaldeh y de. Salicylidene I'iiz~l-~-semicarbccxone, when crystallised from hot alcohol, in which it, is only moderately soluble, yields small, hard, rhombic prisms melting at 252'. It; is moderately soluble in chloroform, methyl alcohol, or acetic acid, sparinglyso in warm benzene and insoluble in light petroleum : 0.1522 gave 17.6 C.C. moist nitrogen a t 18' and 770 mm. N = 13.54. C18H2302N3 requires N = 13.41 per cent. The salicylidene derivative dissolves in dilute aqueous caustic potash, and is reprecipitated on addition of dilute hydrochloric acid. The alcoholic solution with ferric chloride gives an intense green coloration, which is not altered by dilute hydrochloric acid.m-Niti*obenxplidene Pinyl-i,!r-semicai.baxone, separated from the solution as a yellow, viscid solid, which soon hardened and crystallised. It aissolves sparingly in nearly all solvents, forming yellowish-green solutions ; from hot alcohol i t crystallises in pale yellow, small, hard prisms melting at 216". On cooling, itLEACH : A PSEUDO-SEMICARBAZIDE FROM PINENE. 23 solidifies to a clear, glassy mass, then crystallises, and on reheating melts a t a lower temperature : 0.1056 gave 15 C.C. moist nitrogen at 17.5' and 765 mm. N = 16.54. p - Methoxy benx y 1 idene Pin yl-$-semicar baxone, C18H2,03N, requires N = 16.37 per cent. separates from hot alcohol in transparent and well-defined rhombic prisms melting a t 224-225", and remelts at the same temperature.It dissolves readily in warm alcohol, chloroform, or acetic acid, and is sparingly soluble in warm ether or ligbt petroleum, crystallising from the latter in small clusters of prisms; from dilute acetic acid clear flat prisms were deposited, but the odour of the aldehyde was distinctly noticeable in the liquid, owing no doubt to a partial hydrolysis : 0.1622 gave 18.7 C.C. moist nitrogen at 23' and 771 mm. N = 13.16. Ciitnarnylidene Pinyl-$-semicarbaxone, C,,H2702N, requires N = 12.79 per cent. crystallises from hot alcohol in small, colourless prisms melting at 236' with slight discoloration, It dissolves sparingly in cold methyl or ethyl alcohols, but readily in the warm solvents, and crystallises from the former in transparent, four-sided prisms; it is soluble in chloroform or warm benzene, but sparingly so in ether or light petroleum : 0.1504 gave 17.2 C.C.moist nitrogen a t 21' and 766 mm. N = 13.12. C20H2,0N3 requires N = 1 3.00 per cent. Addition of the quinone to the base caused the immediate separation of a bulky, brown crystalline precipitate from the deep red solution. When crystallised from alcohol, dark yellow needles are formed, which decompose a t 194' with evolution of gas. The substance dissolves readily in chloroform, methyl or ethyl alcohol, or acetone, giving deep orange-coloured solutions; it is sparingly soluble in ether or light petroleum, giving bright yellow solutions; i t dissolves also in warm dilute caustic potash to an orange-coloured solution, and on addition of dilute hydrochloric acid a deep green precipitate is obtained. When heated to looo, the colour changes from yellow to orange, and the compound loses weight corresponding to one molecule of water ; two separately prepared specimens were analysed :24 LUMSDEN: THE LIQUID VOLUME OF 0.1644 gave 19.2 C.C. moist nitrogen at 22' and 770 mm. N = 13.40. 0.2126 lost 0.0118 at 100' ; H20 = 5.55. 0.1480 ,, 17.3 C.C. 9 , 19' ,* 766 ,, N=13*54. ClvH210zN3 requires N = 14.04 per cent. C,7H,,0,N,,H,0 ,, Acetone Pin$-+sernicarbaxone.-Addition of acetone to the dilute acetic acid solution of the base gave no precipitate on warming; in dilute ammoniacal solution an oil separated, from which, on standing, the pseudosemicarbazide crystallised. N = 13.24 ; H,O = 5.67 per cent. Action of Nitrous Acid on the Hydrochloride of the pseudo-Xernicarbaxid. The hydrochloride was dissolved in water and cooled to 0' by the addition of ice, and exactly one molecular proportion of sodium nitrite was added. The liquid became turbid, and a white, crystalline pre- cipitate of the pseudocarbamide separated : vH*N(NH2) C7H12<(lMe_--" >CO + HN02 = CH-NH C 7 H , 2 < b ~ e .NH >CO + N20 + H20. The presence of the nitrous oxide was not proved. When the pseudosemicarbazide was dissolved in dilute nitric or hydrochloric acid and sodium nitrite added, a white precipitate separated at first, and soon afterwards a yellow oil which crystallised, and on examination proved to be the nitroso-$-carbamide melting at 161'. ROYAL COLLEGE OF SCIENCE, LONDON, SOVTH KENSINGTON, S. W.