1. Dissolve the sample in distilled water and dilute the solution to any conven-ient brix between 10° and 15°.
2. Mix thoroughly, allow to stand until all air is removed and determine the brix by hydrometer or alternatively by refractometer.
3. Take a portion of the solution prepared in (1) and add:
(a) Sufficient Horne's dry lead sub-acetate to clarify.
(b) a spoonful of dry kieselguhr then filter and collect the Filtrate.
4. Determine the mean saccharimeter reading using a 200 ml polariscope tube.
Calculation
The % Pol is read off table 11 using the mean saccharimeter reading and tempera-ture corrected °Brix by refractometer or the uncorrected °Brix reading by hydrometer. Platinum (or Quartz) dish 100 - Muffle Furnace
125 ml capacity Hot Plate Reagents - Sulphuric acid (conc.)
Procedure
1. Heat Platinum dish to redness in furnace or over burner.
2. Place in desiccator and allow to cool.
3. Weigh the dish on analytical balance.
4. Weigh 5.0 gm of sample into Platinum dish.
5. Moisten sample with 0.5 ml of concentrated sulphuric acid.
6. Heat gently over hot plate until sample is carbonized.
7. Place in Muffle furnace pre-heated to 550°C (1022°F), dull red heat, and incinerate until all carbon is burnt off. (This may require as much as 5 hours).
8. Remove from furnace, cool, and carefully add a few more drops of the con-centrated sulphuric acid.
9. Reheat in Muffle furnace at 800°C (1472°F) for 15 minutes.
10. Remove from furnace and cool in desiccator to room temperature.
11. Weigh Platinum dish with sulphated ash.
Calculation and E.g.
Weight of dish (empty) = 48.3762 gms Weight of dish + sugar = 53.6230 gms Weight of sugar = 5.2468 gms Weight of dish + ash = 48.4056 gms Centrifugal Machine 64.0° Brix Syrup Procedure
1. Place 1000gm. of well-mixed raw sugar in the mixer. Turn the mixer on to low speed.
2. Gradually add 380 ml. of 64.0° Brix granulated sugar syrup at room tempera-ture. (A 64.0 °Brix syrup made from high quality sugar may be substituted for a syrup made from granulated sugar.) The syrup is added slowly from a dispensing burette and must be added at a uniform rate for approximately 4 1/2 minutes.
3. The raw sugar and syrup continue to mix for an additional one minute. The total mixing period is 5 1/2 minutes.
4. Transfer the entire magma at once from the mixer to the Laboratory Centri-fugal Machine.
5. Bring the Centrifuge up to 3000 rpm in 15 seconds and spin at 3000 rpm for exactly two minutes.
6. Remove the sugar from the basket and spread it on a clean surface in a thin layer not to exceed 1/4 inch thick.
7. Immediately after spreading take representative portions totalling approxi-mately 100 gm. from all areas in the spread layer and immerse in 75 ml. of anhydrous methanol contained in a 250 ml. extraction flask. This portion of the sample is to be used for the grain size test.
8. The remaining portion of the spread which is to be used for colour is mixed periodically (by hand) during drying so that at the end of drying, the sample is well mixed.
9. If sample is not to be tested immediately, it should be stored in sealed jars.
C. Colour Apparatus
Spectrophotometer (a 560 nm
Pyrex sintered - glass filter (porosity F) for white sugar Source of vacuum
Buchner type funnel Filter paper
Reagents - Dilute hydrochloric acid (0.1N); Dilute sodium hydroxide solution (0.1N); Kieselguhr (analytical grade).
Procedure
1. Prepare a solution of the sugar to be tested using distilled water. Below are the
concentrations:-(a) White sugar -- 50% solids
(b) Raw Sugar - as high as practicable, consistent with reasonable filtra-tion rates and cell depth.
2. Filter the solution under vacuum with analytical grade Kieselguhr (1% of sugar weight) over filter paper. The first portion of the filtrate should be discarded if cloudy. (While sugar solution and light coloured liquors should filtered through Pyrex sintered glass porosity F without addition of fil-ter aid).
3. Adjust the pH of solution to 7.0 +0.2 with dilute Hydrochloric acid (HCl) ana/or caustic soda (NaOH). (Do not adjust the pH of white sugar solution).
4. Remove entrained air under vacuum.
5. Race the solution in absorption cell. Determine the attenuancy at 560 nm in a spectrophotometer using distilled water as a zero colour reference standard (wavelength of 560 nm for White Sugar).
NOTE:- The length of the cell should be chosen so that the instrument reading will be between 10 and 90% transmittancy.
6 Calculate the attenuation index of the solution as follows:
Total Colour (Attenuation) at 560 nm
= 1000 x optical density
(concentration of solution gm/mm) x (cell size in cm) If spectrophotometer is calibrated fn transmittancy units
then:-Total Colour (Attenuation) at 560 nm
= 1000 ( - log T)
(concentration of sol. gm/ml) x (cell size in cm)
NOTE:- It is important that in neutralizing the solution no more than 10 drops of acid and/or base are used. Total colour is in ICUMSA units.
64
D. Grain Size
1. The flask containing the sample previously collected for grain size test is swirled vigorously for two minutes so that the sugar is well mixed with the solvent.
2. Drain the solvent from the flask. After the solvent has drained, break vacuum, shake the extraction flask and place back over the vacuum flask.
Repeat two or three times.
3. After draining, return flask to an upright position, add 50 ml. of anhydrous methanol and repeat swirling and draining procedure.
4. Repeat swirling and draining procedure twice, using a 50 ml. portion of ethyl ether time. (Caution: Do not use near open flame.)
5. Place drained sugar on absorbent filter paper and allow to air dry. No lumping or caking should occur on drying. Soft conglomerates if any, should be broken by gentle hand pressure. If lumping is observed after drying, discard the sample. Begin again, starting with the affination procedure.
6. Weigh (to ± 0.1 gm.) the entire amount of affined raw sugar which has been washed with solvent and dried.
7. Assemble the screens with a 14 mesh tyler as the top screen, followed by the tyler 20 and tyler 28 mesh screens. A pan, and additional screens if neces-sary, are added to make up a set of screens that will fit on a mechanical shaker.
8. Place the weighed amount of the 14 mesh tyler screen.
9. Place the set of screens on a mechanical shaker and run for five minutes.
10. The grain size, is reported as the percentage of sample passing through the 28 mesh tyler screen, determined as follows:
weight through 28 mesh screen x 100 = % grain size starting weight