RDA ( Recommended Dietary Allowance)

Recommended Dietary Allowance (RDA):

 Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.

How to calculate NPK & Calcium, magnesium and Sulfur in fertilizer

Calcium (Ca), magnesium (Mg), and sulfur (S) are the three secondary nutrients required by plants, but less likely to be added as fertilizer as N, P or K. A standard soil test measures the relative availability of Ca and Mg in soils. There is no accurate soil test for S at this time. A plant analysis is the best diagnostic tool for confirming S availability.

   Excessive use of K fertilizers can greatly reduce the uptake of Ca and Mg. Forage with high K or low Mg concentrations can cause grass tetany, milk fever, hypocalcemia, and other health problems for ruminant animals. 

   Potassium recommendations above the critical level are less than crop removal so as to discourage excessive uptake (i.e., luxury consumption) of K and improve Mg uptake. This can sometimes result in fields rotating out of alfalfa to have depleted soil test K levels.

Determination of Iodine Value (Wijs) in vegetable oil

 Definition of Iodine Value (Wijs) :

 The number of grams of iodine, absorbed per 100 grams of the oil or fat, when determined by using Wijs solution

Principle: 

The sample is dissolved in a non- polar solvent like carbon tetra chloride and after adding with a known excess of iodine monochloride solution in glacial acetic acid  (Wijs solution), it is kept in dark for specified time. Potassium Iodide is then added to it and liberated Iodine is titrated against Standard Sodium thiosulphate solution using starch as indicator.

Apparatus: 

a. Iodine value flask- cap. 500 ml with stopper, 

b. Pipettes, 

c. Burette, 

d. Measuring cylinders

Reagents:

a. WIJ’S solution (Solution of Iodine monochloride in glacial acetic acid): Iodine Mono chloride (ICI) -98  percent  chemically  pure.  Iodine mono chloride Solution-is prepared by dissolving10 ml of Iodine mono chloride in about 1800ml of glacial acetic acid (chemically pure) and shake vigorously. Pipette 5ml of this, add 10 ml of potassium iodide solution and  titrate  with  0·lN standard sodium thiosulphate solution, using starch solution as indicator. Adjust the volume of the solution till it is approximately 0·2N.

b. 10 % KI solution: Prepare a fresh solution by dissolving 10g of potassium iodide free from potassium iodate, in 90 ml of water

c. Starch solution: 5 g of starch with 30ml of cold water and slowly pour it with stirring in to one liter of boiling water. Boil for three minutes. Allow to cool and decant off the supernatant clear liquid.

d. Chloroform or CTC 

e. Std. Sodium Thiosulphate solution: approximately 0·l N.

Dissolve approximately 24.8 g of sodium thiosulphate crystals (Na2S203.5H20) in water which has been well boiled to free it from carbon dioxide and make up to 1000 ml. Store the solution in a cool place in a dark coloured stock bottle. Standardize against  0.1N  Potassium dichromate  solution. Calculate  the normality.

Estimation of Potassium by Flame photometry method

Estimation of Potassium Flame photometry method: 

 Total Potassium are usually determined by dry ashing at 650-700 Degree Centigrade and dissolving in concentrated hydrochloric acid. 

Reagent and Standard 

 (1) Potassium chloride standard solution: Make a stock solution of 1000 ppm K by dissolving 1.909 g. of AR grade potassium chloride (dried at 60oC for 1 h) in distilled water and diluting up to 1 litre. Prepare 100 ppm standard by diluting 100 ml of 1000 ppm stock solution to 1 litre with extracting solution. 

(2) Standard : Pipette 0,5, 10,15 and 20 ml of 100 ppm solution into 100 ml volumetric flasks and make up the volume upto the mark. The solution contain 0, 5, 15 & 20 ppm K respectively. 

Procedure: 

•  Take 5g sample in a porcelain crucible and ignite the material to ash at 650-700 C in a muffle furnace. 
• Cool it and dissolve in 5 ml concentrated hydrochloric acid, transfer in a 250 ml beaker with several washing of distilled water and heat it.
•  Filter the solution and dilute the filtrate 100 ml with distilled water in 100 ml volumetric flask.

 Determine K by flame photometer using the K- filter after necessary setting and calibration of the instrument.

Calculation: Potash (K) %by weight = R X 20 X diluting factor, 

where R= ppm of K in the sample solution 

Determination of Saponification Value in oil

Definition of Saponification Value- The number of milligrams of potassium hydroxide required to saponify completely one gram of the oil or fat.

Principle: The oil sample is saponified by refluxing with a known excess of alcoholic potassium hydroxide solution. The alkali required for saponification is determined by titrating the excess potassium hydroxide with standard hydrochloric acid. The saponification value is an index of mean molecular weight of the fatty acids of glycerides comprising a fat. Lower the saponification value, larger the molecular weight of fatty acids in the glycerides and vice-versa

Apparatus: 

Flat bottom flask .

250 ml, Reflux condenser, 

Water bath

Reagents:

                       Alcoholic Potassium hydroxide solution : Dissolve 35 to 40 g of potassium hydroxide  in  20  ml  of  distilled  water,  and  add  sufficient  aldehyde-free rectified spirit ( conforming to IS:323-1959 Specification for Rectified Spirit (Revised}]to make up to 1000ml. Allow to  stand  overnight,  decant  the  clear liquid and keep in a bottle closed tight with a cork or rubber stopper.

Rectified spirit Phenolphthalein indicator 1 % Hydrochloric acid. 0.5 N

Procedure:

Weigh about 1.5g to 2.0g of the sample into a 250 ml flat bottom flask.Add 25 ml of approximately 0.7 N alcoholic KOH. Connect the  reflux condenser to the  flask. Boil the contents in the flask on the boiling water bath gently and steadily  for  1  hr. Ensure the saponification by absence of any oily matter and appearance of clear solution. After cooling wash down the condenser with 10 ml of neutralized Ethyl alcohol. Carry out the blank at the same time. Titrate with std. 0.5 N HCL using 1 ml phenolphthalein indicator. Prepare and conduct a blank determination at the same time.

Calculation:

Saponification Value= 56.1 X (B- S) x N/W

Where,

B= Volume in ml of std. HCL acid required for the blank 

S= Volume in ml of std. HCL acid required for the sample 

N= Normality of std. HCL acid

W= Weight in grams of the sample taken for the test

Determination of Acid value in oil

Principle: 

The acid value is determined by directly titrating the oil/fat in an alcoholic medium against standard potassium hydroxide/sodium hydroxide. Acid value is a measure of hydrolytic rancidity present in the sample.

Definition: 

Acid value (or "neutralization number" or "acid number" or "acidity") is the mass of potassium hydroxide  (KOH) in  milligrams  that is  required to  neutralize free fatty acids present in  one  gram  of  fat.The  Acidity  of  an oil is expressed  as  oleic acid and  is  measured  by adding neutralized  alcohol  to  the  oil  sample and  titrating  it against 0.1 N sodium hydroxide solution under hot conditions.

Apparatus:

Conical flasks

Burette

Pipette

Reagent:

a. 0.1N Std. Sodium Hydroxide solution

b. Rectified spirit

c. 1% phenolphthalein indicator

Procedure:

Weigh accurately about 5-10g. of oil sample in a conical flask. Add 50 ml to 100 ml of freshly neutralized hot rectified spirit. Add 1 ml of phenolphthalein indicator solution. Boil the mixture for about 5 minutes and titrate while as hot as possible with Std. 0.1N NaOH solution, shaking vigorously during titration.

Calculation:

Acid Value= 56.1 x Vx N/W

Where,

V= Volume in ml of Std. Sodium hydroxide solution. 

N= Normality of Std. Sodium hydroxide solution

W= Weight in gram of sample taken for the test.

Determination of Moisture content in vegetable oil by hot air oven method

Determination of Moisture content in vegetable oil by hot air oven method.

Methodology :IS: 548 (Part I) 1964

Principle

The Moisture Content is measured by keeping an oil sample in an aluminium dish of specific dimensions in an oven at specific temperature. The loss of weight is recorded to calculate moisture content.

Apparatus:

Moisture dish- made of aluminium sheet about 0.45 to 0.56mm thickness, 70- 80mm in

diameter and 20mm deep,provided with tight-fitting slip-over cover.

Desiccator- containing an efficient desiccant.

Air-oven with temperature control device.

Procedure:

Weigh accurately about 10 g of  the  sample  into  dried,  cooled  and  weighed  moisture dish.Place the dish in the Air oven for approximately one hour at 105 + 1°C. Remove the dish from oven, cool in the desiccators to room temperature & weigh.Repeat the procedure, but keep the  dish  in  the  oven  only  for  half  an  hour each time, until the difference  between  the  two  successive  weighings  does  not exceed 1 mg.

Calculation:

Moisture Content % by weight =  100 x w/M

  

Where,

 

w = Loss in weight in gram of the sample upon drying and 

M= Weight in gram of the sample taken for the test.

standardization of 0.1 N NaOH

Standardization is the process of accurately determining the concentration of a solution by comparing it with a solution of known concentration (standard solution). In the case of 0.1 N NaOH standardization, you would need a standard solution of a known concentration, which you can use to determine the exact concentration of NaOH.

Here are the steps for standardizing 0.1 N NaOH:

1. Materials

a. 0.1 N NaOH solution
b. Potassium hydrogen phthalate (KHP)
c. Distilled water
d. Phenolphthalein indicator
e. Burette
f. Pipette
g. Erlenmeyer flask
h. Balance
i. Beaker

2. Procedure:

a. Weigh accurately about 0.1-0.2 grams of KHP in a beaker.


b. Dissolve KHP in about 100 ml of distilled water and transfer it to an Erlenmeyer flask.


c. Add a few drops of phenolphthalein indicator to the solution.


d. Fill the burette with the 0.1 N NaOH solution.


e. Titrate the KHP solution with the NaOH solution until the pink color appears.


f. Record the volume of NaOH used to reach the endpoint.


g. Repeat the titration two more times.


h. Calculate the average volume of NaOH used in the titration.


3. Calculate the exact concentration of NaOH solution using the following formula:

NaOH concentration = (KHP weight x 1000) / (average volume of NaOH used in titration x 204.22)

where 0.1 is the normality of NaOH solution, 1000 is the conversion factor from liters to milliliters, and 204.22 is the molecular weight of KHP.


The calculated concentration of NaOH should be within the range of 0.098 N to 0.102 N. If it is not, then the process should be repeated until you get the desired range.

That's it! Once you have standardized your NaOH solution, you can use it for various analytical purposes.

Written by: AVNI & AAROHI