Chemicals used for the preparation of reagents should be of the highest quality. They should be protected against contamination from dust, moisture, other foreign matter, should be kept in a cool, dry place and be properly labelled.
Acetic Acid
Use - Determination of final molasses purity. Glacial acetic acid, CH3COOH.
Alcohol
Use — Preparation of slurry, saturated mecurtc chloride solution and special analyses.
Ethyl alcohol 95%, C2H5OH Methyl alcohol CH3OH Isopropyl alcohol, 100% CH3CHOHCH3 Alpha — Naphthol solution
Use — Test reagent for sugar in drain waters and condensates.
Preparation
(1) Dissolve 20 gm of analytical reagent grade Alpha - Naphthol in 95% alcohol and dilute to 100 ml.
(2) Store the solution in an amber-coloured bottle.
The dropping bottle used for the reagent should also be amber-coloured to prevent excessive exposure to light.
A fresh solution should be prepared about once per month. The compound looses sensitivity after being opened and exposed to the air.
Alumina Cream (Hydrate of Alumina)
Use — Clarification of juice for Pol determination.
Use b) — Colorimetric determination of silica in boiler water.
Preparation
(1) Dissolve 100 gm of ammonium molybdate in 700 ml of distilled water.
(2) Add 250 ml of ION sulphuric acid solution slowly while stirring and cool.
(3) Add one (1) drop of concentrated nitric acid, HNO3, make up to one (1) litre with distilled water and store.
Asbestos Fiber
Use — To filter Fehling's solutions.
Preparation
(1) Digest a quantity of asbestos on a steam bath with 1:2 hydrochloric acid solution for 48 hours.
(2) Pour onto a Buchner funnel and wash it with four (4) portions of hot distilled water.
(3) Transfer the asbestos back to the beaker and digest with 5% sodium hydrox- ide solution for 48 hours.
(4) Pour onto the Buchner funnel and wash with four portions of distilled water.
(5) Again, transfer the asbestos back to the beaker, add a quantity of 1:2 nitric acid solution and 3 or 4 gm of potassium permanganate crystals, stir well and digest for 36 hours on the steam bath.
(6) Add enough sodium sulfite to reduce all the permanganate, indicated by a change from brown to colourless.
(7) Again transfer to a Buchner funnel and wash with 4 or 5 portions of hot distilled water to remove all soluble material. Continue until the asbestos is free from excess water and dry at 100°C. Store in a wide-mouthed jar.
Buffer Solutions
A buffer solution of pH 7.0 should be used to check the pH meter. However, at times it is necessary to check the meter over a wide range. Therefore instructions are given for the preparation of three different pH ranges.
pH4.65
(1) Weigh on an analytical balance 13.607 gm of sodium acetate (NaC2
H302.3H20).
(2) Transfer to a 1000 ml volumetric flask. Add about 500 ml of distilled water and mix until dissolved.
Ammonium Molybdate solution
Use - Colorimetric determination of phosphates in boiler water and juice.
Preparation
(3) Measure 5.7 ml of glacial acetic acid into the flask and complete to volume with distilled water.
(4) Mix thoroughly. Add 5 drops of chloroform as a preservative and store in a glass-stoppered or polyethylene bottle. The solution will keep indefinitely.
Alternatively Potassium Hydrogen Phthalate (0.05M) may be used.
(1) Weigh on an analytical balance 10.21 gm of dry Patassium Hydrogen Phtha- late (A.R.).
(2) Dissolve in approximately 500 ml of freshly distilled water.
(3) Make up to 1000 ml mark of volumetric flask with distilled water.
pH 7.0
(1) Weigh separately on an analytical balance 3.631 gm of mono-basic potassium phosphate, KH2PO4, and 5.684 gm of anhydrous dibasic sodium phosphate, Na2HP04. l
(2) Transfer both salts to a 1000 ml volumetric flask, add 500 ml of distilled water and mix until dissolved.
(3) Make up to the 1000 ml mark, mix well and add 5 drops of chloroform as a preservative and store in a glass-stoppered or polyethylene bottle.
NOTE - This buffer is rated at pH 6.85 at 25°C.
Temperature
°C
20 25 30 35 40 45
KH Phthalate (0.05 M)
4.00 4.01 4.01 4.02 4.03 4.04
KH2P04
(0.025M) Na2HP04
__(0.025M) 6.88 6.86 6.85 6.84 6.84 6.83
Borax ___O01M 9.22 9.18 9.14 9.10 9.07 9.04
Ca(OH)2 saturated at 25°C_
12.63 12.45 12.30 12.14 11.99 11.84
Cleaning Solutions
(a) Chromic - Sulphuric acid solution Use
Cleaning of laboratory glassware Caustic Potash Solution
Use - Rue gas analyses. Tube B of Orsat Gas Apparatus.
Preparation
Make up a concentrated solution of caustic potash (KOH) of approximately 60° Brix.
Cuprous Chloride Solution
Use — Flue gas analyses. Tube D of Orsat Gas Apparatus Preparation
(1) Weigh out 26 gms of cuprous chloride.
(2) Dissolve in 200 ml of concentrated hydrochloric acid.
(3) Add 120 mis of distilled water and store.
Copper turnings or foil must be added to the storage bottle. It is also impor- tant to add copper turnings to the absorption pipette of the Orsat Gas Appatatus.
Pyrogallic Acid/Caustic Potash Solution
Use — Flue gas analyses. Tube C of the Orsat Gas Apparatus.
Preparation
Make a solution of 5 parts of pyrogallic acid in 50 parts of hot water and 100 parts of caustic potash solution of approximately 50° Brix.
(1) Dissolve 80 gm of potassium dichromate in 300 ml of water heating until the crystals are dissolved.
(2) Cool and add slowly while stirring 460 ml of concentrated sulphuric acid.
CAUTION - Avoid contact of solution with skin or clothing.
(b) Phosphate - oleate solution Preparation
(1) Add 60 gm of trisodium phosphate and 30 gm of sodium oleate to 500 ml of distilled water.
(2) Warm the solution to 70°C and allow the glass to soak in the solution for 15 minutes.
Erichrome Black T Indicator Solution Use - Determination of hardness of water.
Preparation
(1) Add 1 ml of N sodium carbonate to 30 ml of distilled water in a 100 ml volumetric flask.
(2) Then add 1.0 gm of Erichrome Black T and mix.
(3) Make to 100 ml with isopropyl alcohol, mix and store in an amber-coloured bottle.
Fehling's Solution
Use — For the determination of reducing substances.
Preparation
A. (1) Weigh on an analytical balance 34.639 gm of copper sulphate (CuSO4.5H2O).
(2) Transfer to a 500 ml volumetric flask and add distilled water, mix until dissolved and make up to mark.
(3) Allow the solution to stand for two days and filter if necessary through prepared asbestos.
(1) Weigh on an analytical balance 173.00 gm of Rochelle salt (sodium potassium tartrate) and 50.00 gm of sodium hydroxide.
(2) Transfer to a 500 ml volumetric flask and add distilled water, mix until dissolved and make up to mark.
(3) The solution is allowed to stand for two days and filter through prepared asbestos.
The solutions are mixed in equal proportions by volume, immediately before use.
Formaldehyde solution
Use — Preparative for juice samples except those for reducing substances determina- tion.
Reagent grade, 36-38% formaldehyde HCHO.
Hardness Buffer Solution
Use — Determination of calcium and magnesium in water.
Preparation Solution 1
Dissolve 40.0 gm of sodium tetraborate (Na2B4O7.10H20) in approximately 800 ml distilled water.
Solution 2
(1) Dissolve 10.0 gm of sodium hydroxide NaOH and 5.0 gm of sodium sulphide (Na2S) in 100 ml of distilled water.
(2) Cool, mix the two solutions in a 1000 ml volumetric flask and make to mark with distilled water.
Store in an amber-coloured bottle and keep well-stoppered when not in use.
Hardness Reagent Preparation
(1) Dissolve 4.0 gm of disodium ethylene diamine tetra-acetate (Na2CjoHi4 OgN2.2H20) in about 800 ml distilled water.
(2) Add 0.86 gm of sodium hydroxide, NaOH, and make up to 1000 ml in a volumetric flask with distilled water.
Store in an amber-coloured bottle.
Hydrochloric Acid
Hydrochloric acid 36-38% HCl(conc). Specific, gravity 1.18-1.19.
Hydrochloric Acid for Inversion (Jackson & GiDis method)
Chemically pure hydrochloric acid is diluted to a specific gravity of 1.1029 (24.85°
Brix).
Lead Acetate, Basic (Home's Dry Lead)
Use — For clarification of sugar products for analysis.
Preparation
This may be prepared by evaporating to dryness the concentrated solution of basic lead acetate, prepared as described below. The resulting mass is ground to a fine powder in a laboratory mortar.
It should contain 72.8% lead, so that the salt corresponds to a composition of 3Pb (C2H302) .2PbO.
Lead Acetate solution, Basic (Wet Lead)
Use — For clarification of raw sugar for Pol analysis.
Preparation 1
(1) Weigh out 4.30 gm of neutral lead acetate and 130 gm of litharge.
(2) Transfer both chemicals to a litre of distilled water and boil the solution for 30 minutes.
(3) Allow to cool and settle.
(4) Dilute the supernatant liquid to a specific gravity of 1.25 (543° Brix) with freshly boiled distilled water.
Preparation 2
(1) Weigh 360 gm of basic lead acetate, Home's dry lead into 1500 ml beaker.
(2) Add 1000 ml of distilled water. Stir well and boil gently for 30 minutes.
(3) Allow to cool and settle until clear.
(4) Decant the clear liquid and dilute to an indicated 21.9% refractometer solids with distilled water.
Lead Acetate solution, Neutral
Use - Clarifying sugar products for reducing substances analysis.
Preparation
100 gm lead acetate, Pb (C2H3O2)2, are dissolved in distilled water and made up to 1000 ml to give a 10% solution.
Mercuric Chloride
Use — Juice sample preservative Preparation
A saturated solution of mercuric chloride in alcohol is prepared.
Methylene Blue, Solution
Use - Indicator for reducing substances analysis.
Preparation
(1) Weigh 1.0 gm of methylene blue and transfer to a 100 ml volumetric flask.
(2) Fill the 100 ml volumetric flask to the half-way mark with distilled water and dissolve. Make to volume with distilled water and mix well.
Potassium Iodide - Iodate solution, 0.0I25N Use —Determiantion of sulphite in boiler water.
Preparation
(1) Weigh 0.45 gm of Potassium iodate (KIO3) on an analytical balance.
(2) Transfer to a 1000 ml volumetric flask and add 100 ml of distilled water, mix well until dissolved.
(3) Add 4.35 gm of Potassium iodide (KI) and 0.31 gm of sodium bicarbonate (NaHC03). Mix until dissolved.
Complete to volume with distilled water.
Potassium Oxalate, De-leading solution
100 gm of Potassium oxalate are dissolved and make to 1000 ml with distilled water to give a 10% solution.
Phenolphthalein Use — pH indicator Preparation
(1) Weigh 1.0 gm of phenolphthalein powder
(2) Transfer to a 200 ml volumetric flask, add 100 ml of isopropyl alcohol and dissolve.
(3) Add cautiously, drop by drop, 0.1N NaOH until a faint pink colour appears then add one (1) drop of 0.1N sulphuric acid, H2SO4. Complete to volume with distilled water.
INDICATOR TABLE
Name pH Range Colour Change Methyl Orange 3.1 - 4.4 Red to Orange Bromocresol Green 3.8 — 5.4 Yellow to Blue Methyl Red 4.2 - 6.2 Red to Yellow Bromothymol Blue 6.0 - 7.6 Yellow to Blue Phenolphthalein 8.2 - 10.0 Colourless to Red N Sodium Carbonate
Use - To make up Erichome Black T Indicator Solution Preparation
(1) Weigh 53 gm of solium carbonate, special anhydrous.
(2) Transfer to a 1000 ml volumetric flask and fill about half with distilled water and dissolve.
(3) Complete to volume with distilled water and mix.
Sodium Hydroxide Solutions 1. 5% solution approximately.
Use - Preparation of asbestos fibre.
Preparation
(1) Counter-balance a 1500 ml beaker on the dilution balance.
(2) Weigh 50 gm of sodium hydroxide, pellets, NaOH.
(3) Add 950 gm of distilled water.
(4) Stir until dissolved and cool to room temperature and store.
2. N Solution
Use — Determination of acidity in acid cleaning solutions Preparation
(1) Counter-balance a 100 ml beaker on the analytical balance.
(2) Weigh 42.5 gm of sodium hydroxide, pellets, NaOH.
(3) Transfer to a 1000 ml volumetric flask and fill to about half with distilled water. Mix until dissolved.
(4) Cool to room temperature and make to mark with distilled water. Mix thoroughly and store.
3. O.1N Solution Use — Titration of acids Preparation
(1) Weigh 4.3 gm of sodium hydroxide pellets
(2) Transfer to a 1000 ml volumetric flask and fill to about half with distilled water.
(3) Mix until dissolved, cool and make to volume with distilled water. Mix thoroughly and store.
Sulphuric Acid
Reagent - Sulphuric acid, 98% H2SO4 (concentrated), specific gravity 1.84; molecu- lar weight 98.08.
Sulphuric acid solutions 1. ION solution
Use — Preparation of ammonium molybdate solutions.
Preparation
(1) Fill a 1000 ml volumetric flask to about half with distilled water. Place in a bath of cold running water and slowly add 280 ml sulphuric acid while mixing with a rotary motion.
(2) Cool to room temperature, make to mark with distilled water and store.
2. N. Solution Preparation
(1) Fill a volumetric flask to about half with distilled water and add from a burette 29 ml of sulphuric acid.
(2) Mix with a rotary motion and cool to room temperature.
(3) Complete to volume with distilled water.
3. O.IN solution Preparation
Prepare O.l N solution from the above N solution.
Pipette 100 ml of N sulphuric acid solution into a 1000 ml volumetric flask and make up to 1000 ml with distilled water.
4. 0.357N solution
Use — Determination of available CaO in lime Preparation
(1) Transfer 10.2 ml of sulphuric acid from a burette to a 1000 ml volumetric flask containing about 500 ml of distilled water.
(2) Mix and store.
5. 0.02 N solution (N/50)
Use — Determination of alkalinity in boiler water.
Preparation
Pipette 20 ml of N sulphuric acid solution into a 1000 ml volumetric flask con- taining 500 ml of distilled water. Make to mark with distilled water.
CHAPTER IX