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The difference in the percentage of water is 9.03. The quotient of .0903.031 = 3 nearly.

Let us apply these data to the correction of Nos. 18, 19 and 20 in table IV.

I give below these numbers and also their corrections.

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The above corrections were based on the supposition that 53 divisions of the scale correspond to 53 percentage reducing matter when the specific gravity: 1.409 and the percentage water 15.

We may therefore construct the following provisional formulæ, for estimating the correction to be applied to the reading of the scale when the specific gravity of the specimen varies much from

1.409.

Let a reading of scale;
"a corrected reading;

66

= sp. gr. of the sample.

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Then a a3 a (ε 1.409) when the specific gravity is greater than 1.409; and a' = a + 3 a (1.409 — ɛ) when is less than 1.409.

I next propose to undertake some investigations to show the nature and number of the optically active principles present in glucose.

THE EFFECT OF HEATING WITH DILUTE ACIDS, AND TREATING WITH ANIMAL CHARCOAL ON THE ROTATORY POWER OF GLUCOSE; WITH NOTES ON THE ESTIMATION OF CANE SUGAR AND GLUCOSE IN MIXTURES. By H. W. WILEY, of Lafayette, Ind. SHAKING dilute solutions of glucose or grape sugar with animal charcoal produces a slimy precipitate.

I use the words glucose and grape sugar in their commercial sense. By glucose I mean the thick syrup made from corn starch, and by grape sugar, the solid product made from the same sub

stance.

By pure glucose I mean the substances present capable of reducing the alkaline copper solution. I will not take time here to discuss the propriety of these names, nor the exact nature of the substances present.

I have made some experiments to determine the effect of animal charcoal on the rotatory power of the glucose of commerce. The following are some of the results obtained.

In each case 10 grammes of the substance were taken and made up to 100 cc. The observation tube was 200 mm. in length.

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From these figures it is seen that a glucose may lose nearly 10 per cent. of its rotating power when shaken with animal charcoal.

This is a matter of great importance when attempts are made to examine commercial syrups with the polariscope.

These syrups are usually highly colored, and require a great deal of bone black and lead acetate to make them fit for polariscopic examination. I have not yet tried the action of lead acetate on the rotatory power of glucose.

HEATING WITH DILUTE ACIDS.

The following readings as well as those in the preceding part of this paper are divisions on the cane sugar scale.

I.

A glucose gave direct reading................

Heated to 68° with 10 per cent. of its volume of strong sulphuric
acid. Reading...

Loss.........

53°.7

52.96

.74

II.

Heated same glucose for 50 minutes at 68°. Reading....................

502.76

Loss........

2.94

III.

Direct reading another glucose....

43°.36

Heated for 10 min. at 68° with 10 per cent. of its volume strong
HCI. Reading.......

43°.02

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The per cent. of reducing substance in the above sample before
heating with the acid was.

C2°.50

After.......

65 .58

Increase......

3.08

Thus a loss of 4.10 on the cane sugar scale corresponded to a
gain of 3.08 per cent. in reducing power.

VII.

A grape sugar gave direct reading........

40°.83

Heated with its volume strong HCl for 20 min. at 68°. Reading 31.70

Loss......

9.13

Loss.......

VIII.

A grape sugar gave direct reading.........

40°.00

After heating with vol. IICI. for 15 min. at CS°. Reading.............

32 .52

7.48

69°.30

71°.50

2.20

The per cent. of reducing substance in the above was, before
heating

After heating..

Gain......

Thus a loss of 7.48 divisions in rotating power corresponded only
to an increase of 2.20 per cent, in reducing power.

It will be seen, by inspection of the foregoing numbers, that glucose and grape sugar undergo quite a degree of change when subjected to the process of inversion as it is practised on cane sugar.

This change is sufficiently great to introduce an appreciable error into the process of estimating cane sugar and glucose in mixtures.

CONVERSION OF THE WHOLE OF THE OPTICALLY ACTIVE SUBSTANCES IN GLUCOSE INTO PURE MONO-ROTATORY GLUCOSE.

I next made an attempt to convert the whole of the optically active substances, present in glucose, into pure glucose, by prolonged heating with dilute sulphuric acid.

The conversions were made in a flask fitted with a glass tube about one metre in length.

By this device, vapors arising are condensed and flow back into the flask. Thus no loss of volume takes place.

The flask was at first heated in a water bath at 100°.

The conversion, however, took place so slowly by this method, that I afterwards added enough salt to the bath to raise the temperature to 104°.

The sulphuric acid employed was of 1.25 sp. gr., and was used in the proportion of 10 per cent. of the volume of the glucose solution. The readings were made in a tube longer by one-tenth than half of the length of the 200 mm., and the results multiplied

The following table contains the results of my work.

Nos. 1. 2. and 3 were heated at 100°. No. 1 for six hours, No. 2 for four hours, and No. 3 for three hours.

Nos. 4, 5, and 6 were heated for three hours at 102°.

Nos. 7, 8, 9, 10, 11, and 12 were heated for three hours at 104°.

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In all cases the samples assumed a decidedly yellowish tint before the completion of the operation; interfering somewhat with the delicacy of the final readings.

No. 8 was a sample of glucose made for confectioners' use. we exclude it, we get the following general results.

If

1st. The per cent. of reducing substance obtained is nearly 82.00.

2nd. The average reading of the cane sugar scale is nearly 25.5 divisions.

3d. If the pure glucose present is mono-rotatory, the specific 8°.85 X 100 rotatory power would be 0 = = 54 nearly. 8°.85 is 2 X 8.2

the angular rotation visions of the scale.

(half shadow) corresponding to 25.5 diBut the specific rotatory power of pure

glucose for the half shadow in the polariscope is supposed to be

nearly 50. We have then here an excess of ◊ equal to 4.

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