94 



CHEMISTKY. 



in their furnace as much as 20 to 30 kilo- 

 grammes of material, which was subjected to 

 the action of heat for 20 days at a time. The 

 method which yielded the best result is de- 

 scribed as follows: First, there is formed a 

 fusible aluminate, which is heated to a bright 

 red, with a silicious substance ; in this way the 

 alumina is gradually released from its saline 

 combination in the presence of a flux, and it 

 becomes crystallized. The aluminate of lead 

 is found to yield the best results so far. On 

 placing in a crucible of refractory clay a mixt- 

 ure of alumina and minium in equal weights, 

 and keeping it for a sufficient length of time 

 at a bright-red heat, there will be found, when 

 it has grown cool, at the bottom of the crucible, 

 two different layers one vitreous, consisting 

 chiefly of silicate of lead; the other crystalline, 

 and often presenting geodes filled with fine 

 crystals of alumina. These crystals are white; 

 but if the rosy crystals of the ruby are re- 

 quired, there must be added to the mixture of 

 alumina and minium from 2 to 3 per cent, of 

 bichromate of potash. To produce the blue 

 color of the sapphire, we must use a small 

 quantity of cobalt oxide with a trace of bichro- 

 mate of potash. The authors exhibited some 

 crystals of their artificial gems to the Academy. 

 These did not possess the brilliancy of the natu- 

 ral product, because they did not present to 

 the lapidary faces suitable for change or cut- 

 ting. The authors, however, hope to find, in 

 the considerable amount of crystalline sub- 

 stance they have produced, some crystals capa- 

 ble of being cut and cleaved. 



Purification of Hydrogen. Since the time 

 when Rose first proposed the use of hydrogen 

 gas as a reducing agent in analytical opera- 

 tions, a method for its perfect purification has 

 been a desideratum. Schobig has lately made 

 certain experiments in this direction, employ- 

 ing a saturated solution of potassium perman- 

 ganate, with results which appear to be satis- 

 factory. 



The impurities which were introduced were 

 the hydrogen compounds of sulphur, phos- 

 phorus, arsenic, antimony, and carbon. The 

 permanganate was used as neutral, acid, and 

 alkaline solution, contained in a Bunsen wash- 

 bottle. Careful examination of the gas after 

 passing through a layer 10 centimetres thick 

 of the solution, either when only a single im- 

 purity was present or when all were mixed to- 

 gether, failed to show a trace of foreign sub- 

 stance. Hydrogen sulphide was found to be 

 best removed by an alkaline solution; the 

 other substances by a neutral or acid one. 

 Even coal-gas, after passing slowly through a 

 thickness of 10 centimetres of the solution, de- 

 posited no carbon when passed through an ig- 

 nited tube, the carbon being oxidized to car- 

 bon^dioxide. As to the question whether hy- 

 drogen itself is not oxidized by the perman- 

 ganate, the author made comparative experi- 

 ments with neutral, acid, and alkaline solutions, 

 which showed that oxidation does take place, 



the maximum rate being about a third of a 

 cubic centimetre per hour under the condi- 

 tions employed, and this in the neutral solu- 

 tion. With the hydrogen thus perfectly puri- 

 fied the author succeeded in reducing a silver 

 solution, in the dark, and in the absence of or- 

 ganic matter. In dilute solutions the silver 

 separated as a fine powder; in concentrated 

 ones, it formed a mirror. 



Sources and Determination of the Proteids. 

 The doctrine now generally held, that ani- 

 mals do not produce the protein substances 

 which enter into the composition of their 

 bodies, but obtain them from their food, makes 

 the determination of the amount of protein 

 compounds in "vegetables a matter of great 

 physiological, as well as practical, impor- 

 tance. The method usually employed is to 

 deduce the amount of proteids from the per- 

 centage of nitrogen found in the food, by ulti- 

 mate analysis. Profs. Wanklyn and Cooper 

 criticise this method as not only difficult in 

 practice, but one that yields very inaccurate 

 results ; and, as a substitute for it, they pro- 

 pose to measure the protein constituents of 

 vegetables by the amount of ammonia which 

 the vegetables generate when they are sub- 

 jected to the action of a boiling solution of 

 potash and permanganate of potash; and, in 

 fact, have made a special adaptation of the 

 well-known ammonia process of water analy- 

 sis to the case of vegetable protein. They 

 proceed as follows : 



Into a litre-flask a carefully-weighed gramme of 

 the vegetable substance to be analyzed is placed, 

 and 20 cubic centimetres of decinormal solution of 

 caustic potash is added, and then water is added un- 

 til the litre-mark is reached by the level of the 

 liquid. The contents of the flask are then shaken 

 up so as to insure thorough mixture. In this man- 

 ner we obtain a liquid of such a strength that each 

 cubic centimetre contains one milligramme of the 

 flour or other vegetable substance to be operated 

 upon. Ten or 20 cubic centimetres of this liquid 

 (i. e., 10 or 20 milligrammes of the vegetable sub- 

 stance) are convenient quantities to work with. 



The next step is to get the retort in order as for 

 a water-analysis, and to place in it 300 or 500 cubic 

 centimetres of good drinking-waterj and to add 50 

 cubic centimetres of a solution containing 10 grammes 

 of potash and 0.4 gramme of permanganate of potash, 

 and to distill until the residue in the retort no longer 

 yields the slightest trace of ammonia. That having 

 been done, 10 or 20 cubic centimetres of the liquid 

 containing the vegetable substance are to be added, 

 and the distillation proceeded with. The vegetable 

 substance will then be attacked, and its protein will 

 yield ammonia, which will distill over, and may be 

 measured by means of the Nessler tests. 



It was shown, some years ago, that egg-albu- 

 men yields about one-tenth of its weight of 

 ammonia when submitted to such a process as 

 the foregoing, and that solutions containing 

 different quantities of egg-albumen yield am- 

 monia exactly proportional in amount to the 

 strength of the solutions of albumen. The ex- 

 periments of Wanklyn and Cooper show a par- 

 allel result in the case of vegetable protein, as 

 will be seen from the subjoined table, where 

 the ammonia, multiplied by 10, gives a fair 



