374 MTJREXIDE 



and their ethereal solutions are fluorescent to a considerable degree ; but the tint of 

 the fluorescent light of the ethereal solution of rubiacineis orange-yellow, while that 

 of the ethereal solution of munjistine is yellow inclined to green. The examination 

 in a pure spectrum shows that the difference is not due to the admixture of a small 

 impurity, itself yielding a fluorescent solution; but the tints may bo readily con- 

 trasted by daylight, almost without apparatus, by the method I have described in a 

 paper, " On the Existence of a Second Crystallisable fluorescent Substance in the Bark 

 of the Horse-chestnut " (" Quart. Journal Chem. Soc. vol. ii., p. 20). I consider either 

 of the two points of difference I have mentioned sufficient by itself to establish the 

 non-identity of munjistine and rubiacine." 



' The purpurine which I succeeded in extracting from munjeet and in purifying 

 from munjistine in the way already described, formed beautiful dark crimson needles 

 having all the usual properties of that substance. When examined by Professor 

 Stokes, they gave the very characteristic spectra of purpurine. 



' Tinctorial Power of Munjistine and Munjeet. Professor Eunge stated in 1835 that 

 munjeet contained twice as much available colouring-matter as the best Avignon 

 madder. This result was so unexpected, that the Prussian Society for the Encourage- 

 ment of Manufactures, to whom Professor Runge's memoir was originally addressed, 

 referred the matter to three eminent German dyers, Messrs. Dannenberger, Bohn, and 

 Nobiling. These gentlemen reported, as the result of numerous and carefully con- 

 ducted experiments, that so far from munjeet being richer in colouring-matter than 

 ordinary madder, it contained considerably less. This conclusion has been confirmed 

 by the experience of my friend Mr. John Thorn, of Birkacre near Chorley, one of the 

 most skilful of the Lancashire printers. 



' From a numerous series of experiments I have just completed, I find that the 

 garancine from munjeet has about half the tinctoral power of the garancine made 

 from the best madder, viz. Naples roots. These, however, yield only about 30 to 33 

 per cent, of garancine, while munjeet, according to my friend Mr. Higgin of 

 Manchester, yields from 52 to 55 per cent. Taking the present prices, therefore, of 

 madder at 36 shillings per cwt. and munjeet at 30 shillings, it will be found that 

 there will be scarcely any pecuniary advantage in using munjeet for ordinary 

 madder-dyeing. The colours from munjeet are certainly brighter, but not so durable 

 as those from madder, owing to the substitution of purpurine for alizarine. There is, 

 however, great reason to believe that some of the Turkey-red dyers are employing 

 garancine from munjeet to a considerable extent. When this is the case they 

 evidently sacrifice fastness to brilliancy of colour. By treating such a garancine with 

 boiling water, and precipitating by an acid in the way already described, its sophisti- 

 cation with munjeet may very readily be detected. The actual amount of colouring- 

 matter in munjeet and the best madder is very nearly the same ; but the inferiority 

 of munjeet as a dye-stuff results from its containing only the comparatively feeble 

 colouring-matters, purpurine and munjistine, a small portion of the latter being useful, 

 whilst the presence of munjistine in large quantities appears to be positively injurious. 

 So much is this the case that when the greater part of the munjistine is removed from 

 munjeet-garancine by boiling water, it yields much richer shades with alumina mor- 

 dants than before.' 



MOTTTZ'S METAL A brass composed generally of 40 parts of zinc to 60 of 

 copper. These proportions may be somewhat varied, but the above are commonly 

 regarded as the most favourable for rolling into sheets. The metal being properly 

 melted is cast into ingots, heated to a red heat, and rolled into sheathing, and worked 

 into ship's bolts at that heat. It will not work well at a lower heat. This metal 

 was originally patented by the late G. F. Muntz, of Birmingham, in 1832. It has to 

 a large extent superseded the use of copper sheathing, as being cheaper, and at the 

 same time keeping the ships' bottoms cleaner. 



MTTRBX. This genus, belonging to the Mollusca, contains many beautiful shells, 

 from which the Tyrian purple of the ancients was probably obtained. 

 lYTUREX-AN E. The purpuric acid of Prout. 



MUKEXXBZ:. Syn.Purpuratc of Ammonia. C 18 H 8 N 8 12 (C 8 H 8 3WO S ). Murex- 

 ido is one of those substances which, although investigated by many chemists of great 

 reputation, has long been regarded as of uncertain constitution. This is the more 

 remarkable from the fact that, owing to its extreme beauty it has always attracted a 

 large amount of attention. It is invariably formed when the product of the action of 

 moderately strong nitric acid on uric acid is treated witji ammonia. This process, 

 however, is rather valuable as a test of the presence of uric acid than as a method of 

 procuring murexide. Dr. Gregory who has given much attention to the best methods 

 of preparing the substance in question, has published the following formula for work- 

 ing on the small scale :' Four grains of alloxantino and seven grains of hydrated 

 alloxan arc dissolved together in half an ounce by measure of water by boiling, and the 



