Announcement:
Position: Home >> Technology >> View Details
Wall panel production line honor popularization Certificate
AddDate:2012年01月04日    Hits:

   Chloridion among Cement  is coming from raw materias, fuels,mixing raw materials,and the agents。Chloridion in cement is main element causing steel corrosion among the concrete.As steel corrosion is one of main forms causing damage of the concrete,each country has made relevent provision.  Therefore, "≤0.5%grinding aids is allowed adding, chloridion  in cement must be ≤0.06%" as a demand  be added into cement new standard, it embody  cement industry makes promises and responsibilies for quality assurance of the concrete.  About chloridion measuring mehods have so many GB/T176-2008《cement chemical analyzing methods》gives two kinds of measuring methods about chloridion one is ammonium thiocynate volumetric method(basic method); the other is distillation-mercuric nitrate compleximetry(substitute method). Below we will introduce specifically about two methods. 

1 ammonium thiocynate volumetric method

1.1 principle
  Samples must be resolved by nitric acid, at same time, eliminating interference of sulfide. Putting in known amount of silver nitrite standard solution , let chloridion deposit  in the form of silver chloride. After boilling, filtering, put filtrate and cleaning mixture under the temperature of 25℃ . With ferric salt(Ⅲ)as indicator,using ammonium thiocyanate titrate excess silver nitrate.  The transform as follows:
  

chloridion reacted with silver nitrate solution:Cl-+Ag+=AgCl↓
ammonium thiocyanate reacted with excess silver nitrate:CNS-+Ag+=AgCNS↓
  

  1.2 analyzing steps and operating points
 (1)weigh around 5g sample,putting into 50ml water.
 Should mix asap and let sample scatter evenly, otherwise the samples will deposit at bottom of the beaker.      

   (2)While mixing, putting in 50ml nitric acid(1+2), heat and boil.
After nitric acid is added, we must mix it constantly, and boil, let the hydrogen sulfid effuse, so as  not to disturb the testing, at same time, it can let the samples dissolve evenly.
 

   (3)Accurately remove 5ml silver sulfide standard solution into the solution, boil it 1~2 min。
  whether silver sulfide solution is accurate or not determines accuracy of testing result, so the silver sulfide standard solution must be made up strictly, also added by  pipette and burette.

   (4)Adding a little of filter paper pulp. 
  filter paper pulp can not be added so much, so as not to affect the speed of filtering.
  

    (5)Use slow filter paper baptised by nitric acid to take out the air and filter, filtrate will be stored in 250ml conical flask.
  Before filtering, slow filter paper and glass sand core funnel are all baptised by nitric acid(1+100), so as not to cause some testing errors.
 (6)filtrate and lotion, total volume reach around 200ml,so solution must be frozen under 25  ℃ in weak light and darkness.
  Titration must be conducting in room temperature, if the temperature is high, red complex will be easily color fading.  
  (7)putting in 5ml ammonium ferric sulfate indicator solution,using ammonium thiocyanate standard titration solution titrates until the reddish brown is not disppeared during shaking.   
  When titrating, you must shake the solution completely, avoide sediment absorbing silver ion.  

(8)When ammonium thiocyanate standard titration solution consuming volume is less than 0.5 ml, please use half reduced sample quantity to retest. 
  2 Distillation mercuric nitrate compleximetry
  2.1 Priciple
  Using stated distilling apparatus, under the condition of 250-260 ℃,hydrogen peroxide and phosphoric acid as decomposition sample, purified air as carrier, distill and seperate chloridion, using dilute nitric acid as absorbing liquide, distill 10~15 min, using alcohol to wash condenser pipe as well as its lower end  in the conical flask, the adding of alcohol accounts 75% above. Around pH3.5, using two benzene azo carbon hydrazide as indicator, using mercuric nitrate standard titration solution to titrate. The equation as follows: 
         Distillation reaction:3Cl-+H3PO4=HCl↑+PO43-
         Titration reaction:Hg2++2Cl-=HgCl2↓
   The end:Hg2++ two benzene azo carbon hydrazide=Hg- two benzene azo carbon hydrazide(cherry red)
  2.2 Analizing steps and operating points
  (1)adding 3ml water as well as five drops nitric acid
  (a)absorb the hydrogen chloride during heating and distillation.
  (b)eliminate further disturbance of  few of hydrosulphuric acid evaporated.
  (c)let the low end of the pipe contact very well with the liquid surface. 

  (2)weigh sample,put on dried distillation tube, do not make the sample adhere to the tube wall.     if  it has the sample adhere to the tube wall, then it will have some sample no reacting, the testing result will be very low.
  (3)adding 5 drops of hydrogen peroxide, shaking so well.
  (a)scatter the sample, prevent the sample from blocking.
  (b)when distillation, hydrogen sulfide is oxidized into sulfuric acid by hydrogen peroxide, and not to be steamed out. 
  (4)putting in5ml phosphoric acid.
  (a)boiling point of phosphoric acid is relatively high, the ability of dissolving minerals is relatively strong, when decomposing during high temperature, hydrogen chloride will be distilled out.   
  (b)during distillation, it can let the halide and sulfide in the form of haloid acid and hydrosulphuric acid be distilled, dilute nitric acid absorbing liquid is belonging to weak acid, can not absorb.
        
(c)after phosphoric acid added, carbon dioxide out, then connecting the exit pipe and intake-tube.           (d)inorder to accelerating testing speed, reducing the testing time, at the fist group of distillation, you can prepare the second group of sample, after the phosphoric acid  added, then waiting on the tube shelf.           (5)intake and exit tube connection.
        connect the exit pipe first, second connecting intake-tube.
  (6)air flowmeter adjustment
  airflow adjusting speed 100~200 ml/min, at this time there are constant bubble in the conical flask, if there are not, please check out the air tightness.
  (7)distillation time
    distillation time 10~15 min, distilling time can be according to the content of chloridion, when chloride content is 0.2%~1.0%, the time should be 15~20 min,and using larger concentrated mercuric nitrate standard titration solution to titrate. 
  (8)alcohol usage
  usage of the alcohol  is guaranteeing indicator can dissolve completely.

        (9)pH value adjustment。
     BPB indicator color change range is 3.0~4.6, using sodium hydroxide to adjust to be blue, and to be yellow, and drip , at this time the PH value will be just 3.5.

  (10)when make up two benzene azo carbon hydrazide solution , it must be dissolved in alcohol completel, otherwize its sensitivity will be affected. 
  (11)BPB as well as two benzene azo carbon hydrazide is all dissolved in alcohol, so making up is not so much in one time, otherwise will change the density of the indicator, let the end color change and not sharp, and affect the result.    
  (12) mercuric nitrate standard titration solution makes up
  (a) mercuric nitrate solution belongs heavy metal solution and slso toxic,when making up, must wear the glove. 
  (b)to prevent its hydrolysis, when making up, must put into nitric acid, and dilute with water,also must use dry beaker. 
  (c)water absorbability of solid mercuric nitrate is so high, after finish weighning, it must be sealed preservation.  
  (d)no need stoving mercuric nitrate before weighning.  

Home | About Us | News | Products | Company Mien | FAQ  | CUSTOMER INQUIRY | Contact Us
Address:No.42-1 Langmaoshan Road, Jinan City, Shandong Province Postal Code: 250022 Tel: +86-0531-82985999 Fax: +86-0531-82985666
All Rights are Reserved by Shandong Chuangxin Building Materials Machinery Co., Ltd. Lu IC