Preparation of light iron oxide colloid

The preparation of light iron oxide colloid includes principle, operation and matters needing attention.

Principle:

FeCl3+3H2O =Fe(OH)3 (colloid) +3HCl (reaction condition: boiling water heating).

Operation:

Drop 1 ~ 2ml saturated FeCl3 _ 3 solution into boiling distilled water, boil until the liquid turns reddish brown, and stop heating.

Precautions:

1, saturated ferric chloride solution should be used instead of dilute ferric chloride solution in experimental operation. The low concentration of ferric chloride is not conducive to the formation of iron hydroxide colloid.

2. Drop the FeCl _ 3 saturated solution into boiling water, and do not directly heat the FeCl _ 3 saturated solution. If the concentration of the solution is too high, Fe(OH)3 precipitate will be directly generated, and iron hydroxide colloid will not be obtained.

Distilled water should be used in the experiment, not tap water. Because tap water contains impurity ions, it is easy to precipitate the prepared colloid.

4. After the saturated FeCl3 _ 3 _ 3 solution is added to the boiling water drop by drop, it can be heated and boiled slightly. If heated for a long time, it will lead to colloid aggregation.

5. Write the chemical reaction equation for preparing Fe(OH)3 colloid, and mark it with colloid instead of "↓" and "↑".

Brief introduction of light iron oxide colloid and its electrical properties;

1, Introduction

A strong oxidant, such as sodium hypochlorite, can oxidize newly generated iron hydroxide into sodium nitroprusside with oxidation state of+Ⅵ in alkaline medium. Heating gradually decomposes into iron oxide and water. Insoluble in water, ether and ethanol, soluble in acid, the solubility in acid depends on the length of preparation time, and the newly prepared soluble acid is difficult to dissolve if it is left for a long time.

Iron hydroxide can be used to make pigments, medicines, purified water and an antidote to arsenic. Dropping 0.5mol/L hydrochloric acid into the iron hydroxide colloid to agglomerate the colloid first, then dropping the solution continuously, and the precipitate gradually disappeared.

Equation: Fe(OH)3 (colloid) +3HCl=FeCl3+3H2O.

2. Electrical properties

Colloidal particles are charged by adsorbing ions in solution. When positive ions are adsorbed, colloidal particles are positively charged and negative ions are negatively charged. Under different conditions, what kind of ions are easily adsorbed by colloidal particles is related to the properties of adsorbed ions and the surface structure of colloidal particles. Don't say "colloid is charged" because the dispersion system is electrically neutral.