METHOD ALKALIMETRI

1. The manufacture of aqueous ethanol
   mix 500 ml 95% ethanol and 500 ml of pure water which is measured separatelyand the mixture was measured at 25, the volume of a mixture of 970ml.
2. manufacture of ethanol diluted neutral
   on a number of dilute ethanol add 2 - 3 drops of phenolphthalein and 0.1 N NaOH solution until there is a pale pink color.
3. making a solution of phenolphthalein
   200mg phenolphthalein dissolved in 60 ml of ethanol 90% add enough water until100ml
4. manufacture of carbon dioxide-free water
   pure water boil for 5 minutes or so, then covered with cotton fed Cao oxide carbon powder and let stand until cool and can not absorb carbon dioxide from the air
5. manufacture of 0.1 N NaOH solution
   number of NaOH dissolved in CO2-free water so that each 1000 ml solution containing 4.001 grams of NaOH
6. standardization of NaOH 0.1 N
     carefully weigh 400 mg of potassium biftalat previously been mashed and dried at120 * C for 2 hours, enter in the erlenmeyer, add 75 ml of CO2-free water, caperlenmeyer shake until dissolved. add 2 drops of phenolphthalein and titration with NaOH until there is a pink solid.
   
   one ml of 0.1 N NaOH is equivalent to 20.42 mg KHC8H4O4
   reaction:
   KHC8H4O4 + NaOH => KNaC8H4O4
   calculation:
   
   Normality of NaOH = mg KHC8H4O4: (ml NaOH x BM KHC8H4O4)
7. determination of drug levels of salicylic acid
   
   carefully weigh 500 mg, dissolved in 25 ml of aqueous ethanol that has beenneutralized with 0.1 N NaOH, add phenolphthalein and titrate with 0.1 N NaOH
   one ml of 0.1 N NaOH is equivalent to 13.81 mg of C7H6O3
   
   reaction:
   HOC6H4COOH + NaOH => H2O + HO.C6H4.COONA
   
   calculation
   levels of salicylic acid = (ml NaOH x N NaOH x 13.81) : (mg sample x 0.1) x 100%
8. Grafic concentration