96 



CHEMISTRY. 



which may seem, from the analysis, to be 

 worthy of more extended investigation. The 

 amount of moisture is estimated by ascertain- 

 ing the loss of weight on drying a small por- 

 tion of the sample. The crude ash left after 

 ignition is separable into the constituents that 

 are soluble in water ; those that are insoluble 

 in water, but are soluble in dilute hydrochloric 

 acid; and those which, insoluble in those sub- 

 stances, are soluble in sodic hydrate. The resi- 

 due still undissolved consists usually of a little 

 unconsumed carbon. The amount of nitrogen 

 is determined by combustion with excess of 

 soda-lime. Exposure of a part of the sample to 

 the action of pure coal-tar benzole gives the 

 benzole extract, which may consist of volatile 

 oil removable by evaporation ; alkaloids, glu- 

 cosides, and organic acids, soluble in water; 

 alkaloids, and possibly glucosides, soluble in 

 dilute acids; chlorophyl and resins, soluble in 

 80 per cent alcohol; and wax, fats, and fixed 

 oils which do not yield to either of the solvents. 

 The part of the plant not dissolved by benzole 

 is further treated with absolute alcohol, and 

 afterward with other agents, as water, snb- 

 acetate of lead, and dilute hydrochloric acid, 

 as special tests. The part which remains in- 

 soluble, after treatment in alcohol, is exposed 

 to the action of water; that part still remain- 

 ing insoluble is boiled in concentrated sulphu- 

 ric acid, for the conversion of starch, etc., into 

 dextro-glucose. Boiling the residue from this 

 treatment with sodic hydrate gives an extract 

 containing albuminous matter, modifications of 

 pectic acid, Fremy's " cutose," coloring, humus, 

 and decomposition products. The crude fiber 

 from this process, treated with chlorinated soda, 

 bleached, and dried, leaves a residue of cellu- 

 lose. Treatment with benzole, 80 per cent 

 alcohol, and water, removes from nearly all 

 plants the constituents of greatest chemical 

 and medicinal interest. In analyses of food 

 materials the compounds extracted by dilute 

 acids and alkalies have great value. 



A NEW DIGESTIVE AGENT. In a paper be- 

 fore the French Academy of Sciences, M. Wurtz 

 has drawn attention to the great chemical and 

 therapeutical value of a substance called pa- 

 paine, which possesses the property of exciting 

 the digestive function. It is derived from the 

 juice of the common papaw-tree (Carica papa- 

 ya), which belongs to the family of the Cucur- 

 bitaceve, or gourds. The milky juice which con- 

 tains the papaine is slightly bitter and styptic, 

 free from tartness, but with a weak acid reac- 

 tion, and is so highly charged with albumen 

 that Vauquelin compared it to blood deprived 

 of its coloring matter. It flows from incisions 

 made in the bark and the green fruits, and is 

 immediately bottled and sent to market, either 

 pure or with the addition of ten or twelve per 

 cent of alcohol to prevent fermentation. If 

 pure, it becomes coagulated; if mixed with 

 alcohol, it remains liquid, and, after standing, 

 separates into a clear liquid and a white pre- 

 cipitate, composed in great part of albumen, 



fi brine, and a considerable quantity of precipi- 

 tated papaine. Alcohol precipitates from it 

 crude papaine ; this, after being washed in al- 

 cohol and ether, to remove fatty matters, is 

 again dissolved in water. The precipitate from 

 this solution is pure papaine, which, when puri- 

 fied by dialysis, has the composition of an al- 

 buminoid substance. Papaine, refined with the 

 subacetate of lead, offers several distinctive 

 characteristics, among which are: 1. It is very 

 soluble in water, dissolving like a gum ; 2. The 

 solution makes a lather with water; 3. The 

 solution becomes turbid in boiling, without co- 

 agulating ; when it is curdy it sometimes leaves 

 an insoluble residue in water; left to stand, 

 the solution becomes turbid after some days, 

 and a microscopic examination shows it to be 

 filled with vibriones; 4. In the presence of a 

 saccharine liquid, papaine acts as an alcoholic 

 ferment with an extraordinary energy and 

 promptitude, but the digestive property may 

 be arrested by the application of benzoic or 

 salicylic acid. The most important property 

 of papaine, and one which puts it in the rank 

 of the most powerful digestive ferments, is its 

 action on meats. One part of papaine will di- 

 gest and transform into soluble peptone from 

 two hundred and fifty to three hundred parts 

 of meat. Its solubility in different fluids al- 

 lows it to be used in a great many pharmaceu- 

 tical forms ; and, being a vegetable juice, it can 

 be preserved with more stability than animal fer- 

 ments, and can be kept indefinitely when dry. 

 EEPOET ON PHOTOMETEIO STANDARDS. The 

 committee appointed by the British Board of 

 Trade to examine and report upon the different 

 standards of photometric measurement which 

 have been proposed for adoption, as well as upon 

 the standard now used for testing the illuminat- 

 ing power of coal-gas, have made a report re- 

 commending the standard air-gas flame of Mr. G. 

 Vernon Harcourt as the most exact and trust- 

 worthy. This flame is produced by burning 

 a mixture of air with that portion of Ameri- 

 can petroleum which, after repeated rectifica- 

 tions, distills at a temperature of 50 C. or 122 

 Fahr. The portion is almost entirely com- 

 posed of pentane, and is used in the propor- 

 tion of one volume of pentane at 60 Fahr. to 

 576 volumes of air. The flame is brought to 

 a height of two and a half inches with a burn- 

 er a quarter of an inch in diameter. The light 

 is quite uniform, the extreme difference obtained 

 by two observers in nineteen observations be- 

 ing 0'3 of a candle, or 1/8 per cent. The com- 

 mittee found candles very objectionable as stand- 

 ards, and subject to a maximum variation in 

 115 determinations of 22'7 per cent between 

 two pairs of candles. Messrs. Keates and Sugg's 

 plan for burning sperm-oil with a two-inch 

 flame from a circular wick was found subject 

 to sudden variations; and Mr. Methven's sys- 

 tem of allowing only a particular part of a 

 three-inch coal-gas flame to pass to the pho- 

 tometer was not considered sufficiently exact 

 for the work required of it. 



