Vocabulary

2. Match the words from the text with the meanings (1-7) below:

a. bud 1. something that remains

b. twig 2. to say something is true

c. residue 3. a small structure that contains flowers orleaves

d. to resemble 4. a glow of reflected light

e. tinge 5. to be similar to

f. luster 6. a slight trace of colour

g. to claim 7. a small shoot

Reading

3. Read the text and find answers to the questions below:

1. What was the year of thallium discovery?

2. Who named the element “thallium” and why?

3. What group of chemical elements is thallium associatedwith?

4. Where is thallium placed in the Mendeleyev table?

5. What colour has this element when it is exposed to air?

Thallium

Thallium made its public debut in 1862 at the InternationalExhibition in London. The year before W. Crookes searching byspectrography for tellurium in the residues of a German sulfuric acidplant noted an unaccountable green line in the spectrum. Heconcluded that this line represented a new element.

With a poetic touch he compared the colour of the spectrumline to the bright green tint of new vegetation and named the elementthallium from the Latin thallus – “a budding twig”. He wassuccessful in obtaining a small quantity in metallic form for displayat the 1862 International Exhibition in London. Controversies have often arisen as to the priority of a discovery,and thallium was no exception. Professor A. Lamy, workingindependently of W. Crookes, observed the same spectrum line in theresidues from another sulfuric acid plant and claimed credit for itsdiscovery. W. Crookes was, probably, prior to A. Lamy in discoveryand preparation by only a few months.

W. Crookes' assumption that thallium belonged to the sulphurfamily was soon disproved as the physical and chemical propertieswere investigated. Studies revealed that the element was closelyassociated with lead, mercury, potassium and aluminum. Mendeleyevwhen publishing his atomic table placed it in Group III under indiumbetween mercury and lead; and this has been its accepted place ever

since.

Thallium is found in potash minerals, which have nocommercial significance at present. Today the metal is recoveredmainly as a by-product from the roasting of pyrite ores in theproduction of sulfuric acid and from the smelting of lead and zinc.

Metallic thallium when freshly cut has a metallic luster, whichupon exposure to air dulls to a bluish grey tinge resembling lead inappearance. As a matter of fact, the properties of thallium are verysimilar to those of lead.

Investigations of the systems of thallium and other elementsshow that thallium readily alloys with many other elements, theexceptions are copper, zinc, aluminum, nickel and selenium.

Speaking

4. Arrange the following sentences according to the logic of the text:

1. It is often discussed who is the first to discover a newelement, and thallium was no exception.

2. Thallium didn’t belong to the sulphur family because of thephysical and chemical properties.

3. Professor A. Lamy was the first to discover a new element.

4. Lead and thallium stand near each other in the atomic table.

5. Investigations show that thallium doesn’t alloy with zinc.

5. Work with a partner. Persuade your partner that is it difficult to bea discoverer of a new metal using the information from the text.

UNIT XVIII

How do you say?

Before you start

1. What do these abbreviations stand for? Match the abbreviations inthe box with the full forms (1-9) below:

1.centimeter a) km

2 gram b) ml

3. cubic c) kg

4. square d) m

5. kilogram e) cm

6. kilometer f) g

7. liter g) (x)²

8. meter h) l

9. milliliter i) (x)³