Division 7.2 Values of the inversion factor Q

The following formulae give accurate values for Q, for various sources of light with corrections for concentration and temperature:

Sodium light and polarimeter with angular degrees:

Q

0,8825 + 0,0006 (C — 9) — 0,0033 (T — 20).

Mercury green light and polarimeter with angular degrees:

Q

1,0392 + 0,0007 (C — 9) — 0,0039 (T — 20).

White light with dichromate filter and saccharimeter with international sugar scale degrees:

Q

2,549 + 0,0017 (C — 9) — 0,0095 (T — 20).

In the above formulae:

C

Percentage of total sugars in the inverted solution as polarized,

T

Temperature of the inverted solution in the polarimetric reading.

Note 1:

The percentage of total sugars C in the inverted solution may be calculated from the direct reading and the change on inversion in the usual manner, using the usual values for the specific rotations of sucrose, lactose and invert sugar.

The correction 0,0006 (C — 9) etc., is only accurate when C is approximately 9; for normal condensed milk, this correction can be neglected, C being close to 9.

Note 2:

Variation in temperature from 20 ^oC of 1 ^oC makes little difference in the direct reading, but variation of over 0,2 ^oC in the invert reading necessitates a correction. The correction - 0,0033 (T — 20) etc., is only accurate between 18 ^oC and 22 ^oC.