实验报告英文版

The determination of nitrogen content in the ammonium saltFormaldehyde method

一、The experiment purpose

1、To study the application of acid base titration

2、Master the formaldehyde method principle and the method for determination of nitrogen content in the ammonium salt

3、The use of master the volumetric flask and pipet

二、The experimental principle

Because NH4 acid is too weak to directly with NaOH standard solution titration, we usually using formaldehyde is transformed into titratable acid:

4NH4++6HCOH=CH26N4H++3H++6H2O

Products, hydrogen ions and CH26N4H+ can be directly for accurate titration,titration product CH26N4 is weak alkaline, so using phenolphthalein as indicator.

According to the volume of the consumption of sodium hydroxide, may be calculated in proportion of nitrogen content in the ammonium salt:

wN=CNaOH·VNaOH·M/m×100%

三、Instruments and reagents

Equipment and materials:The alkali type buret50ml，Conical flask250ml，Volumetric flask100ml，pipette20ml，Measuring cylinder10ml，A beaker100ml，Analytical balance，Glass rod

Drugs and reagents:Sodium hydroxide standard solution0.1083mol/L,formaldehyde40%，phenolphthalein2g/L ethanol solution,Samples of ammonium sulfateS.

四、The experimental steps

1、Accurately according to 0.60 ~ 0.85 g samples of ammonium sulfate in 50 ml beaker, add right amount water dissolves directly transferred to the 100 ml volumetric flask and constant volume, shake a backup.

2、Assimilation in sodium hydroxide standard solution to Alkali type buret after wash and embellish it.

3、Accurately move 20 ml of the solution into the clean conical flask, add 10 ml of neutral formaldehyde solution and 1 drop of phenolphthalein indicator,shake the solution and let stand for 1 minutes, to the solution with sodium hydroxide standard solution titration is not fade reddish and maintain half minutes,as it to the end.

4、Observe and record the volume of consumption of sodium hydroxide

5、Parallel determination of three times, calculate the nitrogen content in the sample and the relative average deviation dr≤0.3%

五、The experimental results and data processing

1 2 3

V1/ml 0.86 18.95 17.11

V2/ml 18.95 37.06 35.90

△V/ml 18.09 18.11 18.11

wN/% 20.99 21.01 21.01

WN=20.99%+21.01%+21.01%/3=21.00%

d=0.01%+0.01%+0.01%/3=0.01%

dr=d/wN=0.01%/21.00%×100%=0.05%.