4 66 



SCIENCE. 



a higher percentage of alcohol than dextrose, and in the 

 proportion of 51 to 48. Whether dextrine is fermentible 

 or not has long been a subject of bitter discussion. The 

 weight of authority seems to be in favor of its fermenta- 

 bility by a slow conversion into dextrose. Thus by fer- 

 mentation we are not sure of getting the amount of dex- 

 trose present even when maltose is absent. From this it 

 appears that the process of fermentation is likely to give 

 less reliable results than reduction affords. 



3d. Precipitation with alcohol is even less reliable than 

 the method just given. Alcohol of 90 per cent ceases 10 

 give a precipitate long before the dextrine is all converted 

 into dextrose, as every grape sugar maker well knows. 

 If absolute alcohol is used, dextrose is also precipitated. 



Anthon has shown 19 that fifty parts of alcohol of 

 .83 sp. gr. will only dissolve 1 part of dextrose. Am thing 

 like an accurate separation, therefore, by this method is 

 impossible. 



As an illustration of the variations in the composition 

 of different specimens of amylose I will cite the following 

 analyses by Steiner 20 : 



I. II. III. IV. 



Water 15-5° 6.00 13 30 7.60 



Ash .30 250 .40 1. 10 



Dextrose 45-4° 26.50 76.00 



Dextrine 9.30 15 90 .... 39 80 



Maltose 28 00 40 30 5.00 42.60 



Carbo-hydrates 1.50 7.00 5.30 8.90 



My own analyses have given results quite as puzzling 

 as the above, although I have never been able to satisfy 

 myself with such exact expressions of percents. 



I have heretofore been glad when, by hard work and 

 liberal guessing, I could come any way near the truth. 

 The author ot the above table leaves us in charming ig- 

 norance of the methods by which such accurate percents 

 were obtained ; at least, of methods which would stand 

 the test of criticisms, while the bunching of all the un- 

 knowables as carbo hydrates is quite worthy of the rea- 

 soning of the Concord School of Philosophy. I have 

 given enough, I think, to show the untrustwcirthiness of 

 methods now in use, and of the results obtained by them. 

 I am sorry that I have nothing very much, if any better, 

 to propose as a substitute. What I have been able to 

 accomplish I will now briefly describe. 



THE ANALYSIS OF AMYLOSE. 



Water. I have estimated water in a flat platinum dish. 

 Only two or three grammes should be taken, though in 

 many of my analyses I have used more. This dish is 

 placed in a second one, and this in a paraffine bath 

 heated to I50 Q -I70 . The object of the second dish is 

 to keep the wax from touching the dish which is to be 

 weighed. After two hours the weight is sensibly con- 

 stant, and the whole mass is quite brown. I believe the 

 method will give the water to within one-half of one per 

 cent. 



Ash. There is only one method of determining the 

 ash, i. e., by incineration in a shallow platinum dish in 

 a muffle. The per cent of ash in a strait amylose is 

 extremely small. In most cases its quantity may be 

 neglected as far as practical purposes are concerned. 

 The determination of the ash is chiefly useful to furnish 

 a clue to the purity of the sample. 



Reducing Matter. I determine by Fehling's solution. 

 It will be found most convenient to take 10 g. in 1000 

 c. c. In all cases the volumes of the solutions employed 

 should be as nearly the same as possible. 



Rotating Power is determined by using \og. of the 

 amylose in 100 c. c. If 26,048 £\ are taken the weight 

 of cane sugar, which gives 100 divisions on most 

 polariscopes, the rotation is so great that the neutral 

 point is thrown entirely beyond the graduation. In 

 many cases of high conversion, however, this would not 

 be the case. If the solution is turbid it must be classi- 



,0 Zcitsch. f. d. Gesch. Brauwesen, 1879, No. 11, p, 339. | 

 (ii). (These proceedings Vol. 28, p. 317.) 



fied by blood charcoal, or plumbic acetate. These sub- 

 s'ances, as I have shown ( 21 ), tend to diminish the 

 rotating power. The clearer definition, however, of the 

 neutral point in part compensates for this loss in gyratory 

 power. 



In the light of the foregoing resume it is possible to 

 explain the results of my own work, although I am far 

 from thinking that anything better than approximate per 

 cents can yet be obtained. 



We have seen that an ordinary amylose. whether liquid 



or solid, contains about 86 per cent of material not 



water. One per cent, nearly, of this is ash and optically 



non-active matter. Ten grammes of amylose, therefore, 



will contain an average of 8.5 grammes optically active 



matter. If this were all dextrose it would give in 100 c.c. 



an angular rotation of 8°.67. This is obtained by the 



t 1 . 8 X V 



formula a = _ — 



lX!f. 



Here «,-. = sp. rot. power for yellow ray. 

 B — angular rotation. 

 V = volume of solution in c.c. 

 % = length of observation tube. 

 W — weight of substance in grammes. 



In a large number of cases where I heated the amy- 

 lose with dilute sulphuric acid from 4 to 6 hours, I ob- 

 tained an average value of #=8°. 85. This shows that 

 prolonged boiling does not convert all the amylose into 

 homogeneous dextrose. 



If the substance under examination were all maltose 

 the value of a s would be 135 36 and 6 would become 

 23 nearly. The highest number I ever obtained for an 

 amylose was 22 .24. This shows that even this speci- 

 men, with such a high rotating power contained some 

 matter in a weaker degree of optical activity. 



Finally, if all the snbstances present were dextrine, I 

 would Dot be able to tell theoretically what its rotating 

 power would be, since we have just seen that dextrine is 

 assigned different degrees of activity by different authors. 

 As a mean of these I think we may place dextrine aj 

 = 176°, although I do not wish to be understood as 

 stating its real value. 



This would give a total angular deflection of 2Q Q nearly. 



The problem of analysis is therefore at the present time 

 in the following status : 



1. In every amylose there are present at least three 

 kinds of optically active matter, viz., dextrose, maltose 

 and dextrine. 



2. There are present in every amylose two kinds of re- 

 ducing matter, viz., dextrose and maltose. 



3. A high reducing power shows a high percentage of 

 dextrose present. 



4. A high rotating power, which is always shown when 

 the reducing power is low, indicates a large percentage of 

 maltose and dextrine. 



5. From a very extended series of analyses, I will say 

 that there is no method known which will give reliable, 

 or rather exact, numbers for the percentage of the differ- 

 ent constituents. 



6. I propose to attempt the accomplishment of this 

 very desirable result by first polarizing and then reduc- 

 ing the sample, and then repolarizing the residue. The 

 difficulties of preserving a standard volume and of getting 

 a solution sufficiently clear for polarization have prevented 

 me hitherto from obtaining any results. I hope to over- 

 come these troubles and to establish thereby a reliable op- 

 tical method of determining the percentages of dextrose, 

 maltose and dextrine in amylose. 



Prof. Cantoni has been appointed director of the meteor- 

 ological observatory, to be erected at Pavia. Observations 

 are to be made on the influences of light, heat, and elec- 

 tricity upon vegetable growth, in addition to the ordinary 

 meteorological and magnetical work. 



^.»»Ding. Jour., CLV., p.;«i. 



