Ammonium persulfate is used to intensify the polymerization processes, as well as for condensation in the process of producing rubbers, plastics and latexes, in photography, during etching of printed circuit boards. The specified substance is sometimes used for disinfection and bleaching.
Ammonium persulfate: physicochemical properties
The chemical reagent is a colorless plate crystals, sometimes having a greenish tint. Slightly soluble in H2O (42.7%) at a temperature of 15.5 ° C. In the process of heating above 120 degrees, it forms ammonium pyrosulphide, while oxygen is released. It should be noted that dry salt can last almost unlimited time, while wet salt quickly hydrolyzes with the release of oxygen and nitrogen. Aqueous solutions of this compound begin to hydrolyze even at room temperature; with increasing temperature, the decomposition process intensifies. In order to slow down decomposition, potassium alum or alkali metal sulfates are added to aqueous solutions of ammonium persulfate.
Ammonium Persulfate: Synthesis
The reagent is obtained by electrolysis of a solution of ammonium sulfate in sulfate acid. To do this, take a jar with a diameter of 20 centimeters and a volume of two liters, pour 1.7 liters of a saturated solution of ammonium sulfate and five milliliters of sulfate acid into it. Next, the resulting mixture is subjected to electrolysis using electrodes made of platinum wire. If during the electrolysis it starts to smell like ammonium hydroxide, then add three to five ml of a saturated solution of ammonium sulfate in sulfate acid. After every three to four hours, the current turns off and the electrodes are wiped. After 24 hours of electrolysis, add 90 g of triturated ammonium sulfate and continue electrolysis for another 70 hours. During electrolysis, the solution is regularly stirred. The resulting crystals of ammonium persulfate are separated, and the solution is again saturated with ammonium sulfate and acidified with sulfate acid. The precipitate formed is dried at a temperature not exceeding 40 degrees.
As a rule, the preparation obtained by the indicated method contains no more than 90% sulphurous ammonium; it is often used as an oxidizing agent. A reagent with a lower concentration of the active substance can be recrystallized. For its implementation, 700 g of salt is dissolved in an identical volume of warm water (about 40 ° C). Next, using a folded paper filter, the analyzed solution is filtered off, after which the filtrate is cooled. The obtained crystals of purified ammonium persulfate are sucked off on a Buchner funnel and washed with water. The resulting preparation, as a rule, meets the requirements for reagent qualifications of analytical grade.
Ammonium persulfate is explosion and fire safe, but it contributes to the ignition of other substances. In the process of burning, it releases irritating and toxic substances. Contact of this reagent with flammable substances is unacceptable, since it belongs to strong oxidizing agents and reacts with flammable materials, as well as with reducing agents. During heating, ammonium persulfate quickly decomposes, and many toxic and corrosive gases (nitrogen oxides, ammonia vapors, sulfur oxides) are released. By the degree of impact on the human body, it belongs to the substances of the third hazard class. The maximum allowable dose in the air of the working area for ammonium persulfate is 0.1 mg per cubic meter.
Ammonium persulfate is irritating to the skin, as well as to the mucous membranes of the nasal, oral cavities, respiratory tract, and conjunctiva. Inhalation of the indicated substance provokes the development of asthmatic disease. With prolonged or repeated contact, dermatitis, eczema occurs, which are often accompanied by allergic reactions, manifested in the form of nettle fever and shock.
When working with a reagent, it is necessary to use a variety of personal protective equipment (respirator, rubber goggles, protective clothing).