IX .  Выучите следующие слова и словосочетания:

compound – соединение

alkali metal – щелочной металл

the Periodic Classification – периодическая классификация

 soluble – растворимый

affinity – свойство, родовое сходство

widely distributed – широко распространенный

to employ – употреблять, применять, использовать

corresponding – соответствующий

to the extent of – до степени

lime – известь

brine – морская вода, соляной раствор

saturated with – насыщать, нейтрализовать

under pressure – под давлением

decomposition – распад, разложение

sodium chloride – хлорид натрия

precipitation – осаждение; осадок

X.  Прочтите и переведите текст А.

Text A. Compounds of Sodium and Potassium

The alkali metals — lithium, sodium, potassium, rubidium, and caesium—which fall in Group I of the Periodic Classification, are the most strongly electro-positive elements known. They are all univalent, and their compounds are soluble in water. The metals themselves are distinguished by their great affinity for oxygen. They undergo oxidation rapidly on exposure to air and decompose water readily in the cold, with evolution of hydrogen and formation of soluble, strongly alkaline hydroxides. All these characteristics are most marked in caesium, and least in lithium.

Sodium and potassium compounds are widely distributed and abundant. Lithium compounds are found in comparatively small quantities, and rubidium and caesium are decidedly rare elements. The compounds of sodium and potassium are very widely employed in pharmacy, and corresponding compounds of the two metals are similar in therapeutic action.

Compounds of sodium. The chief naturally occurring compound of sodium is the chloride, NaCL, which is present in sea-water to the extent of 2 to 3 per cent, and is also found as rock salt.

The manufacture of sodium carbonate, sodium bicarbonate, and sodium hydroxide forms the chief branch of the great alkali industry. Most of the sodium salts used in pharmacy are made from the carbonate or hydroxide.

Sodium hydroxide. Contains not less than 95.0 per cent of total alkali, calculated as NaOH, and not more than 2.5 percent of Na₂CO₃.

Sodium hydroxide is manufactured by heating sodium carbonate with water and lime in large iron tanks.

Most of the sodium carbonate produced at the present day is manufactured by the ammonia-soda process. The principle of the method is simple. Strong brine containing a high concentration of ammonia is passed through a "carbonating tower" where it is saturated with carbon dioxide under pressure. The ammonia and carbon dioxide decomposition with the sodium chloride causes the precipitation of sodium bicarbonate, which is not very soluble in water, and is still less soluble in brine.

 

Words:

1. affinity — хим. сродство. Здесь: Эти металлы распознаются по их свойству легко соединяться с кислородом

2. on exposure to air — под действием воздуха

3. iron tanks — металлические емкости

4. "carbonating tower" - «углеродная колонка». (Кавычки означают, что словосочетание не является термином, а используется терминологически в данном тексте)

5. sodium and potassium – натрий и калий

XI.  Answer the questions:

 

1. What kind of metals are lithium, sodium, potassium and caesium?

 

2. In what group of the Periodic Classification do these metals fall?

 

3. When do these metals undergo oxidation rapidly?

 

4. Why are sodium and potassium compounds of great importance in pharmacy?

 

 5. What compounds are found in comparatively small quantities?

 

6. What is the chief naturally occurring compound of sodium?

 

7. How is sodium hydroxide manufactured at present?

 

                                                            TASKS

I. Read and translate the text B: