Tieng anh nganh hoa

the crucible is brought to 1500 - 1700 0 C. As a result all the alk. elements are converted to chlorides. This
reaction is completed after several min. Later complete dissolving of the salts from the crucible requires
about 3 hrs. and requires no control. The soln. obtained is analysed photometrically. One difficulty
encountered was the masking of the emission from K by an excess of Ca. An expt. was made in order to
learn the relation between amt. of K extd. and time of fusion. Microcline was used as the mineral. It was
found that complete extn. of K could be attained by a 3 - 4 min. fusion. A study of reproducibility of
results was made by using Microcline, muscovite and biotite. Av. error did not exceed 0.97 relative %. In
comparing the rapid new method with the usual methods for detg. K in minerals, It was found that the K
content obtained was higher with the new method. Preliminary studies on using the new method in rock
analysis have given entirely satisfactory results. A sketch of the app. is shown, and some data are given in
tables.
EXERCISES
A. Read and translate into Vietnamese
detn.= determination, decompn.= decomposition, generator, temps.= temperature, crucible, anhyd.=
anhydride, graphite, furnace, quartz tube, alk.= alkaline, convert, dissolve, masking, emission, excess,
photometrically, amt.= amount, extd.= extracted, extn. extraction, av.= average, expt.= experiment, soln.=
solution, detg.= determining, app.= apparatus
B. Answer the following questions
1. What is the rapid method for determination of potassium?
2. What are the particle size of mineral sample after grinding?
3. Tell some steps of preliminary studies on using a new method in rock analysis?
4. Write and read all words in abbreviations in the lesson.
C. Translate into English
1. xác nh Kali có mt phng pháp nhanh da trên s phân hy qung trong CaCl 2 nóng chy.
2. Mu qung c nghin nh thành các ht có kích thc t 0,25 - 0,15 mm.
3. Phn ng này kt thúc sau ít phút.
4. Mt thí nghim c tin hành bit mi quan h gia lng K tách ra c và thi gian nóng
chy ca nó.
UNIT 23 : THE USE OF RADIOACTIVE ELEMENTS AS TRACERS
An extremely valuable technique for research that has been developed in recent years is the use of
both radioactive and non-radioactive isotopes as tracers. By the use of these isotopes an element can be
observed in the presence of large quantities of the same element. For example, one of the earliest uses of
tracers was the experimental determination of the rate at which lead atoms move around through a
crystalline sample of the metal lead. This phenomenon is called self-diffusion. If some radioactive lead is
placed as a surface layer on a sheet of lead, and sample is allowed to stand for a while, it can then be cut
up into thin sections parallel to the original surface layer, and the radioactivity present in each section can
be measured. The presence of radioactivity in layers other than the original surface layer shows that lead
atoms from the surface layer have diffused through the metal.
Perhaps the greatest use for isotopes as tracers will be in the field of biology and medicine. The
human body contains such large amounts of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, etc.
that it is difficult to determine the state of the organic material in the body. An organic compound
containing a radioactive isotope, however, can be traced through the body. An especially useful
radioactive isotope for these purposes is carbon 14. This isotope of carbon has a half-life of about 5000
years. It undergoes slow decomposition with emission of beta rays, and the amount of the isotope in a
sample can be followed by measuring the beta activity. Large quantities of C 14 can be readily made in a
uranium pile, by the action of slow neutrons on nitrogen. The process can be carried out by running a
solution of ammonium nitrate into the uranium pile, where it is exposed to neutrons. The carbon which is
made in this way is in the form of bicarbonate ion, and can be precipitated as barium carbonate by adding
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