Silver nitrate measurement:
One: regents and solutions
1. Preparation of silver nitrate solution: 17.5 g silver nitrate was solved in 1000 ml water and agitated evenly in a brown bottle.
2. Preparation of 0.5% potassium chromate solution: 0.5g potassium chromate was solved in 100 ml water.
3. Preparation of 1% starch solution: 1g soluble starch in 10ml water was poured into 100 ml boiling water under agation, boiled mildly for two minutes and aspirated the surfactant aqueous solution for use.
Two: determination
0.2g oven-baked standard sodium chloride (weighed to 0.0002g) was solved in 70ml water, then added in 10ml 1% starch solution, after that the mixture was titrated with 0.1 silver nitrate under agitation and shield, finally added 3 droplets of 0.5% fluorescene indicator for continual titration near the end point until the solution showed pink.

g=the quality of the sample
V=the quantity of the silver nitrate solution

Three: Measurement of choline chloride content:
0.7 g sample was placed in a 100ml volumetric flask, water-scaled and agitated, placed for 20 minutes and filtrated, 6 st potassium chromate was added to 50 ml above-mentioned filtrate aspirated precisely and titrated with 0.1N silver nitrate, the result of titration was corrected with blank titration. The end point of titration showed wine red.
 
V= the cubage of the silver nitrate solution used
N=the equiv of the silver nitrate
g =the weight of the sample



Reinecke salt precipitation method:
One: Reagents
1, Preparation of 10：1 methanol-methyl chloroform solution: added 100 ml methyl chloroform to 1000 ml methanol.
2, Preparation of Reinecke salt: 4g Reinecke salt was solved in 100ml methanol.
Two: measurement of choline chloride content
Weighed 1g oven baked sample precisely and added 100 ml 10：1 methanol and methyl chloroform combined solution, agitated for 30 minutes and filtrated, secondly aspirated 10 ml solution and vapourized to dry under 50℃ water-bath, thirdly added 40ml distilled water cooled to below 5℃ under ice-bath, fourthly added 10ml Reinecke salt and agitated for 30 minutes, placed 30 minutes, after that, the solution obtained in the fourth step was removed to a glass sand-cored funnel being dried for 2 hours and vacuum filtrated, washed the residue with distilled water for three times with 10 ml per time, then washed the residue three times with 5ml methanol per time, and baked for two hours in a 105℃constant temperature oven, finally remove the solid, cooled to room temperature in a dryer and weighed.

m2:the weight of the deposit and glass tundish after drying in oven
m0:the invariable weight of the glass tundish
m1:the weight of the sample

Perchloric acid measurement:
One: Preparation of perchloric acid-glacial acetic acid solution:
Poured 8.5 ml perchloric acid into 500ml glacial acetic acid and 20ml acetic anhydride combined solution under agitation, then added 470ml glacial acetic acid and agitated.

Determination:
Placed 0.2000 g potassium hydrogen phthalate (dried for 2 hours at 105℃) in a dry erlenmeyer and added 20ml glacial acetic acid under warm temperature, and titrated by addition of 4-5 droplets 0.2% crystal violet to change the color of the solution from purple to blue.


Two: measurement of choline chloride content in the dust:
Placed 0.7g (weighed to 0.002g) absolute-dried sample and 40ml methanol in a 250ml erlenmeyer and agitated for 30 minutes firstly, secondly filtrated, thirdly washed the sediment three times with 20 ml, 15 ml, and 15 ml methanol, respectively, fourthly combined the filtrates for further filtration, fifthly vapourized to dry under water-bath and ready for use. After vapourization, solved the residue in 20ml glacial acetic acid under heating, then 2 ml acetic anhydride, 10ml mercuric acetate, and 2 droplets of crystal violet indicator were added under agitation, titrated with 0.1N perchloric acid standard solution until the solution showed pure blue, meanwhile, the result was corrected with blank test.

Crude protein measurement:
One: reagents and solutions
a, Methyl red-bromocresol green mixed indicator: 40mg methyl red and 1g bromocresol green were solved in 60ml 95% alcohol.
b, Copper sulfate-potassium sulfate mixed reagents: the ratio of copper sulfate and potassium sulfate was 6/100.
c, 2 % boric acid solution: 2g boric acid was solved in 100ml distilled water.
d、40% Sodium hydroxide solution：40g sodium hydroxide was solved in 100 ml distilled water.

Two: digestion
Weighed 0.5 g sample precisely (weighed to 0.002g) and placed in a 500ml dry Kjeldahl flask, secondly added 5g copper sulfate-potassium sulfate mixed reagents and 8 ml strong sulfuric acid, thirdly place the combined solution in a hood (a smalle funnel was placed at the mouth part of the flask), heated until all the carbonized particles in the flask were disappeared. After the digestive solution showed lightgreen, continual to heat for about 10 minutes, generally, the digestive time will be equal to or shorter than 30 min. Alternatively, a drying tube could be inserted in the flask mouth to connect the glass pump replacing of the rubber tube to remove the corrosion gases.

Three: distillation
20ml distilled water was added slowly after the solution was cooled, then removed into a 100ml volumetric flask, water-scaled and agitated as sample-decomposed solution, added 2 droplets mixed indicator in 20ml boric acid solution, dipped the end of the cooling tube of the semi-micro distillation in the water of the distillation generator, several droplets of methyl red indicator and several droplets of sulfuric acid should be added to keep the solution with orange color, otherwise more sulfuric acid should be added. Removed 10ml such solution precisely and poured into the reactioner of the distillation and washed the sample inlet with trace distilled water, shut up the inlet glass stopper and added 10ml 40% sodium hydroxide solution, carefully pulled out the glass stopper allowing the sodium hydroxide solution to flow into the reaction chamber, shut up the glass stopper and sealed the inlet with water to avoid gas-leakage. Distillated for 4 minutes made the end of the cooling tube separate from the adsorption solution surface; then distillated for a further 1 minutes, and washed the end of the cooling tube with distilled water, and all the rinses should be removed to the distillate.

Four: titration
Amonia-absorption solution was titrated with 0.05N hydrochloric acid standard volumetric solution immediately, the solution would change from aquamarine to grey red at the end point.

V2: the cubage of the normative hydrochloric acid consumed
V0: the cubage of the solution consumed when titrate blank
W: the weight of sample

The content of the choline chloride :