CHEMISTRY. 



95 



approximation to the actual quantity of vege- 

 table protein in the different samples. 



As will he observed, the experiments include 

 many descriptions of wheaten flour, pea, rice, 

 maize, oats, barley, malt, rye, and arrowroot. 

 The last named is important, as showing a 

 very small proportion of protein. 



Samples of wheaten flour : 



Percentage of 

 NAME OF SAMPLE. Ammonia. 



1. Cambridgeshire extra-superfine 1 . 10 



2. Other samples 1 .00 



8. Household flour, Waterloo Bridge 1.18 



4. Countryflour 1.08 



5. Huntingdonshire 1 .05 



6. Suffolk 1.00 



7. Hungarian 1.10 



8. Another Hungarian 1.05 



9. " " 1.07 



10. Darblay, Paris 1 .05 



11. Vienna 1.08 



12. Australian 0.92 



18. Californian 1 . 18 



14. American 1 .14 



15. Another American 1.17 



16. " " 1.09 



Pea-flour 2.80 



Kice " 0.62 



Maize" 1.08 



Oats 1.00 



Barley 1.10 



Malt 0.50 



Kye 1.45 



Arrowroot 0.08 



In looking through this table the reader will 

 be struck with the constancy of the quantity 

 of protein substances in wheaten flour. If one 

 of the American samples (No. 15) be excluded, 

 it will be seen that the highest percentage of 

 ammonia given by any sample of flour is 1.14; 

 and, excluding the solitary sample of Austra- 

 lian flour, the lowest yield of ammonia is 1.00. 

 Wheaten floor would therefore seem to yield 

 between 1.00 and 1.13 per cent, of its weight 

 of ammonia when subjected to the above pro- 

 cess ; and, according to the rule above given, 

 would seem to contain from 10.0 to 11.3 per 

 cent, of protein compounds. Maize, oats, and 

 barley, as will be seen, very closely resemble 

 wheaten flour in the yield of albuminoid am- 

 monia. Rye, on the other hand, is exception- 

 ally rich in protein. Apparently it is the most 

 nitrogenous cereal. 



The high percentage of ammonia from pea- 

 flour will attract attention ; and, applying the 

 rule, pea-flour contains 23.0 per cent, of pro- 

 tein, which accords with what is known of the 

 pea. The protein in rice amounts to about 

 naif as much as in wheaten flour. 



New Process for the Detection and Determi- 

 nation of Thein. Mr. A. Winter Blythe pub- 

 lishes the following as an improved process for 

 the detection and quantitative determination 

 of thein, either as a means of identifying 

 minute fragments of thein-bearing plants, or 

 estimating the percentage of the alkaloid that 

 such plants contain : The lenf or fragment is 

 boiled in a very small quantity of water, and 

 the little decoction is transferred to a watch- 

 glass, a minute quantity of calcined magnesia 

 added, and the whole evaporated nearly to 

 dryness on the water-bath ; the extract is next 



transferred to the surface of a thin circular disk 

 of microscopic covering-glass ; on this again is 

 placed a thickish ring of glass, which is covered 

 with a second circular disk of thin glass, the 

 whole forming what may be called " the sub- 

 liming cell ; " the subliming cell is placed on 

 the surface of an iron plate, which carries a 

 cup of mercury in which is inserted a ther- 

 mometer, and the plate is fitted in the ordinary 

 way to a retort-stand. This method of subli- 

 mation, in all its essential features, is identical 

 with the one proposed and employed years 

 ago by Dr. Guy. On heating the iron plate, 

 first, moisture is given off and condenses on the 

 cover of the subliming cell, and this cover may 

 be removed and replaced by a second; in a 

 very short time after it has become dry, a light 

 mist is seen on the upper disk, and this mist 

 the microscope resolves into beautifully distinct 

 little crystals of thein they may be identified 

 as "thein" by resubliming, when it will be 

 found they will rise to the upper disk at about 

 the temperature of 101 Cent. The subliming 

 temperature of the extract itself is rather 

 variable ; the extract should be heated, if no 

 mist or crystals become visible, up to as high 

 as 220 Cent., and, if still no crystals are ob- 

 tained, the substance most certainly contains 

 no thein. For a quantitative determination, 

 not less than one gramme, or more than two 

 grammes of either tea or coffee, in its undried 

 state, is as finely powdered as possible, and 

 treated in a flask, with 70 c.c. of water ; the 

 flask is attached to a reversed Liebig's con- 

 denser, and the liquid boiled for one hour; the 

 decoction, including the powdered substance, 

 is transferred to a porcelain dish; about the 

 same weight of calcined magnesia as the sub- 

 stance originally taken is added, and the whole 

 evaporated down nearly to dryness; the pow- 

 dery extract is now transferred to the iron 

 subliming plate already spoken of, and covered 

 with a tared glass funnel, the edge of which 

 must be accurately ground, and the tube of 

 which must be several inches long. The sub- 

 stance should form a very thin equal layer 

 within the circle of the funnel, which may be 

 easily accomplished by a series of gentle taps. 

 The heat at first should not exceed 110 Cent. ; 

 then, when the substance appears thoroughly 

 dry, it may be gradually raised to 200 Cent., 

 and toward the latter stages up to 220 Cent. If 

 the heating has been properly regulated there 

 will be no distillation of empyreumatic prod- 

 ucts, but the alkaloid sublimes, in the cool part 

 of the funnel, in a compact coating, cone-shaped, 

 of beautifully white silky crystals. In order 

 to ascertain when the sublimation is complete, 

 the tared funnel may be cooled and weighed nt 

 intervals, or a series of tared funnels may be 

 kept on hand, and changed until no more thein 

 is extracted. The funnel, as well as the thein, 

 as may be expected, at the end of the process 

 is perfectly dry, and the increase of weight is 

 thein pure and simple. From one to two 

 grammes may be considered by some too small 



