70 



POPULAE SOIEIsrCE NEWS. 



[May, 1888. 



gas The strong acid thus formed appears to at- 

 tack the glass, and it was found that nearly six 

 per cent of the total mass of glass threads em- 

 ployed had been disintegrated. The long-con- 

 tinued apparent condensation was therefore really 

 slow chemical action. Nay, more: when the glass 

 had been dried at a high temperature, no appreci- 

 able condensations of carbonic acid on the surface 

 took place in eight days. A small quantity of 

 water was then introduced, and absorbed by the 

 glass threads with a rapidity which showed that 

 when really dry they acted as a more powerful 

 desiccator than calcium chloride. Immediately 

 after the introduction of the water, the absorption 

 of the CO2 began as before, which proved that 

 moisture was necessary to produce the phenome- 

 non, or that carbonic acid does not condense to a 

 measurable amount on dry glass. — Chemical News. 



CHLORIDE OF NITROGEN. 

 A STRIKING new experiment, exhibiting the 

 terribly explosive nature of chloride of nitrogen, is 

 described by Professor Victor Meyer. A few drops 

 of the yellow chloride were prepared in the usual 

 manner, — by inverting an exceptionally thin flask 

 filled with chlorine gas in a leaden dish containing 

 a solution of ammonium chloride. Instead, how- 

 ever, of gently agitating the apparatus so as to 

 cause the drops to fall into a smaller leaden capsule 

 placed beneath the mouth of the flask, they were 

 allowed to float freely upon the surface The 

 whole apparatus was then enclosed in a cover-box 

 fitted with stout plate-glass sides, through the top 

 of which was passed a bent pipette, turning up be- 

 low just under the mouth of the flask, and con- 

 nected outside with a dropping funnel containing 

 chloride of ammonium solution and a few drops of 

 turpentine. When suflicient chloride of nitrogen 

 had collected, the tap of the funnel was carefully 

 turned so as to allow a little turpentine to slowly 

 rise in the flask. After a moment or two it 

 reached the surface, and mingled with the chloride 

 of nitrogen, causing a brilliant flash of light and a 

 loud explosion, which Professor Meyer likens to a 

 thunder-clap, so much more powerful is the detona- 

 tion in a confined space. The flask, of course, was 

 shattered, not into powder, but into tolerably large 

 fragments : the plate-glass box, however, even 

 afterinany repetitions of the experiment, remained 

 intact; a small door on the side away from the 

 observers having been left ajar so as to prevent 

 any notable increase of pressure. Curiously, the 

 chloride of nitrogen never entirely exploded ; a part 

 remained in the disorted leaden dish, and main- 

 tained an incessant fusillade for more than a 

 minute. — Nature. 



ASBESTOS FOR FILTRATION. 



W. Fresenius reports that he has found finely 

 picked asbestos to be the best medium for facili- 

 tating the filtration of viscid liquids. He found it 

 especially valuable in filtering solutions of pepton- 

 ized liquids, such as are produced by the action of 

 any of the digestive ferments, and which it is next 

 to impossible otherwise to filter through paper. 



He states that he had previously made use of 

 this useful property of finely divided asbestos 

 when he was occupied with the determination of 

 the water-soluble portion of a very fine flour used 

 as infants' food. It had been impossible to obtain 

 a clear filtrate until asbestos was tried, when there 

 was no difliculty whatever. 



He states that he has recently succeeded in 

 accomplishing the filtration of similar liquids by 

 diluting with a considerable proportion of water, 

 and then incorporating with the mixture a small 

 quantity of previously ignited finely picked asbes- 



tos, and thoroughly shaking. After about twelve 

 hours all suspended matters will have deposited, 

 and the liquid may be easily removed by means of 

 a siphon. The operation of washing and shaking 

 is repeated once or twice with fresh water, and the 

 whole mixture finally passed through a glass fun- 

 nel, the neck of which contains a pellet of asbestos. 

 If the first portion of the filtrate runs off cloudy, 

 it is poured back until it is clear. Fresenius states 

 that he allowed the residue in the funnel to become 

 tolerably dry, after which he removed it for the 

 purpose of determining the amount of nitrogen by 

 Kjeldahl's method. Any matter adhering to the 

 funnel can easily be wiped off by means of a small 

 pellet of asbestos, and added to the rest. — Drug- 

 gists' Circular. 



— • — 



A SUBSTITUTE FOR HYDRAULIC CEMENT. 



According to a statement of Mr. Miles, a well- 

 known engineer, it is a fact peculiar to Spanish 

 countries that ordinary brick-dust, made from 

 hard-burned, finely pulverized bricks, and mixed 

 with common lime and sand, is universally and 

 successfully employed as a substitute for hydraulic 

 cement. Mr. Miles says, that, during an engineer- 

 ing experience of some six years in Cuba, his op- 

 portunities were ample for testing its merits; and 

 he found it in all respects superior to the best 

 Rosendale hydraulic cement for culverts, drains, 

 tanks, or cisterns, and even for roofs. In an ex- 

 periment to test the strength of this product, it 

 was found that a block of it half an inch in thick- 

 ness, without sand, and after immersion in water 

 for four months, bore, without crushing, crumbling, 

 or splitting, a pressure of fifteen pounds per square 

 inch. If is thought that by the addition of pul- 

 verizing mills to brick-yards, to utilize the waste 

 and broken bricks, a profitable manufacture might 

 he carried on. — Light, Heat, and Power. 



[Original in Popular Science JVewg.] 

 A TEST FOR SACCHARIN. 



BY L. D. KA8TENBINE, M.D. 



As saccharin may be used to adulterate sugar, 

 a method of separating and identifying may not 

 prove uninteresting to some of your readers. 



Being a sulphur compound, and soluble in ether, 

 the writer employed the method suggested by II. 

 Reischauer, and finds it the best in actual prac- 

 tice. All that is necessary is, to treat the sugar 

 with about three times its volume of ether in a 

 closed vessel for twelve hours, with frequent agita- 

 tions. The etherial solution is drawn off and evap- 

 orated, and the residue carefully ignited in a 

 crucible with carbonate and nitrate of sodium, 

 whereby the saccharin will be converted into sul- 

 phate of sodium, and can be estimated as barium 

 sulphate. Care must be used in igniting, as ex- 

 plosions occur from too intense heat. 



PRACTICAL RECIPES. 



Fixing Indian Ink. — Indian ink, as most of 

 our readers know, is composed of the finest ivory- 

 black and a gelatine size, and is excellent for plans 

 and drawing until any color " wash " — or even a 

 little dampness — comes near the lines, when they 

 then either "blur" or "run" altogether. This 

 may be prevented by di.'-solving in the water used 

 for rubbing up the ink with, about eight grains of 

 bichromate of potassium, or six and a half of 

 the corresponding ammonium salt per fluid ounce. 



Red Stains for Leather. — (1) Dissolve one 

 ounce cochineal in half-pint of hot water, and add 

 one gill of spirits of hartshorn. (2) Bright Crim- 

 son is prepared from alum or tin salts and a 

 decoction of cochineal. (3) Scarlet. — Scarlet 



berries (bruised), 1.05 ounces, dissolve in 4.2 

 ounces alcohol, e'ghty per cent strong, and filter. 

 (4) Red. — Shavings of red Brazil-wood are 

 placed in a bottle, 2.2 pounds wine vinegar is 

 poured over them, and digested for eight days, and 

 stirred frequently in the mean while. The solution 

 is then filtered through a cloth. Meantime a 

 solution of 1.05 ounces alum, free from iron, in 

 8.75 ounces water, is prepared, and the above prep- 

 aration of Brazil-wood is added to this under con- 

 stant stirring. A very beautiful red is obtained in 

 this manner. The shavings of Brazil-wood may 

 also be boiled in rain-water, and this to be com- 

 pounded with a solution of bitartrate of potash. 



To TAKE Impressions from Seals. — To take 

 an exact model of any coin, medal, embossed 

 stamped paper, or, in fact, any device raised or 

 imprinted, cut a piece of cardboard, with which 

 form a ring just the dimensions of the impression 

 to be taken, then pour within the said ring melted 

 fusible metal. The carding will prevent the metal 

 from running away, and in a few minutes it will 

 cool, and the impression taken will be the same 

 as the original, but reversed. Fusible metal is a 

 compound of eight parts of bismuth, five of lead, 

 and three of tin, which liquefies at the same tem- 

 perature as boiling water. 



RAILROAD NOTES. 



A New Boiler Covering. — At the Rhode 

 Island Locomotive Works a number of new engines 

 are being built that are lagged all over boiler and 

 dome with an asbestos mortar that is easily applied^ 

 and makes the job all one piece. The preparation is 

 put on while the boiler is under steam, and a couple 

 of days are needed to apply it properly. It is claimed 

 that it is not necessary to remove it when the engine 

 goes into the shop, as the least leak is shown through 

 it, and a piece can be cut out, the leak repaired, and 

 replastered. It cannot fail, says an exchange, to 

 be a better job than wood, and is fire-proof. 



Parchment Bearings. — Experiments are 

 being made on Prussian railways with axle boxes 

 fitted with bearings of vegetable parchment in place 

 of brass. The parchment is strongly compressed 

 before being used; and it is thoroughly dried, to 

 prevent subsequent shrinkage. . Wooden rings are 

 placed on the outside of the bearings, fitting the 

 collars of the journal. An emulsion of water and 

 oil, and all the mineral oils, are used as lubricants. 

 The parchment soon becomes impregnated with oil, 

 and is able to go a long time without a renewal of 

 lubrication. It is between the body of the journal 

 and the thin edge of the parchment segments that 

 friction takes place. The claim is made that these 

 compressed paper bearings make a tough material 

 that is superior to metal. Such bearings are also 

 in use in a German sawmill with satisfactory 

 operation. 



Railway to Teheran. — Accounts received 

 from the Caspian describe the railway from Resht 

 to Teheran as being already in hand, the engineers 

 being on the spot, and material commencing to 

 arrive from Europe via Batoum and the Trans-Cau- 

 casian Railway. The line is being constructed by 

 a Belgian syndicate, enjoying the warm support of 

 the Russian Government. It is expected that the 

 undertaking will be rapidly completed, the Shah as 

 well as the Russian authorities being impatient in 

 this respect. At present it is not contemplated to 

 push the line any farther ahead ; but plans exist 

 for extending it eastward to Meshed and south to 

 the Persian Gulf. As regards the former, it is pro- 

 posed afterwards to carry it on to Herat and India. 

 This, when the section from Baku to Resht, is also 

 finished, will open a new route to India from the 

 Black Sea. 



