CHEMISTRY. 



93 



lows: 1. 68 parts of pulverized nitrate of 

 . iL 1 .!' charcoal, of light texture; 20 of 

 jlycerino. 2. 70 parts of baryta, as 

 I ' of powdered rosin, 20 of nitro- 

 '.iii-. The clmrroal should by carl>onized 

 low temperature, and, consequently, still 

 iu hydrogen. An addition of 5 to 8 

 r i-riit. of sulphur to either of the above 

 i:\tures gives a powder which fires more 

 ri-ikly, lint, at the same time, it increases the 

 : in the manufacture, carriage, and ap- 

 il'u-ation of the powder, which should not bo 

 i^ht of. The method of using these 

 > \\-ilers is to place them in cartridges, like 

 irework-cases, covering the powder with a 

 ittlo fulminant, mercury for example, before 

 closing and priming. The cartridge has merely 

 placed in the hole, and covered in the 

 usual manner, and it may be fired either by a 

 fuse, or the electric spark ; in either case the 

 fulminating powder, acting on the nitro-gly- 

 cerine, inflames the whole of the contents 

 instantaneously. To render carriage of the 

 cartridges less dangerous, a little ordinary 

 gunpowder may be substituted for the mer- 

 curial fulminant. 



The owners of the Nora-Gyttorp Mills, Swe- 

 den, have invented a new kind of powder, con- 

 taining, it appears, a mixture of nitrate of am- 

 monia and nitrate of potash, with other ingre- 

 dients not known to the public. This material 

 is, according to some accounts, a more power- 

 ful explosive than nitro-glycerine, and cannot 

 be ignited, or made to explode, but by the im- 

 pact of a blow, or a falling weight, or by the 

 detonation of a small cartridge containing 

 common gunpowder. Experiments made at a 

 military establishment at Berlin with this pow- 

 der have proved that, while ordinary gunpow- 

 der, gun-cotton, nitro-glycerine, and dynamite, 

 took fire the moment flame is approached, this 

 powder does not do so. As regards the effect 

 of the impact of a blow of a falling weight 

 (the same, of course, in each case), ordinary 

 gunpowder requires for explosion that the 

 weight fall from a height of between 4 and 5 

 'feet; nitro-glycerine, 1| foot; dynamite, 2J 

 feet; and ammonia gunpowder, between 12 

 and 15 feet. A sample having been sent to 

 France from Berlin, did not, the author says, 

 confirm the high opinion this substance ia 

 thought worthy of in Pruasia. 



Chemical Changes of Hides into Leather. 

 The Annales de Chimie et de Physique, for 

 July, contains on essay by M. A. Miintz on the , 

 composition of skin, in which he mentions 

 experiments, undertaken by him, to deter- 

 mine, from a theoretical point of view, the 

 changes taking place in the conversion of 

 hides during the process of tanning. Annexed 

 is a summary of the paper : 



A piece of ox-hide which was being converted into 

 leather for the soles of boots was selected as the most 

 appropriate for the investigation, and the operations 

 were commenced after cleansing and depilation. In, 

 1 1 recesses no chemical change would take place, 

 except, perhaps, iu cases in which lime is employed 



in tin) dcpilntion, a small quantity of which L do- 

 jf.Mti-il in the skin, but afterward removed by a 

 solution of glucose. The following process of twilling 

 consists in stooping the bides in an acid liquid for A 

 time varying from three weeks to two or three 

 month*. Tliis acid liquid contains acetic and lactic 

 acids, and a small quantity of tannin : its effect ia t 

 distend the pores of the epidermis, and thus facili- 

 tate the subsequent process of tanning. During tho 

 swelling so much water and other substances aro 

 absorbed that the bide increases in weight to such 

 uii extent that it is now as heavy as it was b<Tr<; 

 the cleaning and depilation, the audition of dry mat- 

 ter amounting to nearly 19 per cent. ; a small quantity 

 of mineral matter is lost, the augmentation being duo 

 to the addition of carbon, hydrogen, and oxygen. 

 After eleven months in the tan-pit an increase of 

 nearly 83 per cent, was observed ; a small diminu- 

 tion in the quantity of nitrogen took place, while 

 the mineral constituents, and carbon, hydrogen, and 

 oxygen, were augmented. The organic materials 

 added nad exactly the same composition as those 

 absorbed by the hide during swelling, but they ditfer 

 much from the composition of tannin. Tho author 

 believes that the loss of nitrogen during the tanning 

 process is due to a decomposition or part of the 

 leather, for ammonium salts were found in the liquor 

 from the tan-pits. The structure of leather is also 

 very diiferent from that of skin ; while the latter is 

 fibrous, the former is spongy ; skin will absorb three 

 or four times its weight of water, swelling considera- 

 bly, but leather scarcely absorbs one and a half time 

 its weight, and without increase of volume: 100 

 parts of skin by treatment with boiling water leave 

 8.35 of insoluble matter, the rest being converted 

 into gelatine ; tho residue from leather under the 

 same circumstances is about 48 per cent. The com- 

 pound obtained by the action of tannic acid on gela- 

 tine differs very much in composition and properties 

 from leather. A description is given of a process for 

 the estimation of tannic acid: and M. Muntz an- 

 nounces the observation that tie residue, after boil- 

 ing skins with water, contains a substance dissolved 

 by Schweitzer's cupro-ammoniacal reagent, and thus 

 resembling cellulose, but containing about 15 per 

 cent, of nitrogen. The author next gives an account 

 of the composition of the mineral substances present 

 in skin ana in leathers, and points out the changes 

 produced during the tanning. He concludes that the 

 tannic acid is partially converted into more oxi- 

 dized compounds, as gallic acid, glucose, lactic, ace- 

 tic, formic, carbonic acids, and most probably pro- 

 pionic acid, the remaining less oxidized residue con- 

 verting the skins into leather. 



Preparation of Anthraeen. Dr. J. Gessert 

 gives what he considers to be the best method 

 of preparing anthracen, as follows: Anthra- 

 een is found in that portion of the distillation 

 of coal-tar, commonly called "green grease," 

 which is composed of about 80 per cent, of 

 the heavy oil naphthaline, and 20 per cent, of 

 anthracen. The semifluid grease is first 

 placed in a centrifugal machine, in order to 

 expel, mechanically, as much as possible of 

 the oil; tho residue is heated to 40, and 

 pressed, preferably between hot plates. The 

 cake thus obtained (crude anthracen, contain- 

 ing 60 per cent, of that substance) is purified 

 by boiling with light tar-oil (coal-tar naphtha), 

 or with petroleum naphtha. The pasty mass 

 is again placed in the centrifugal machine, to 

 remove the last traces of heavy oil, and the 

 material next submitted to sublimation. In 

 order to test the green grease for the quantity 

 of anthracen, from 5 to 10 grms. of that sub- 



