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The Chemistry Library uses the Library of Congress Book Classification Scheme.

How to find books using Library of Congress (LC)

LC class marks, also known as call numbers, are alphanumeric. They are composed of: 

  • the class or subject identifier
  • the item number
  • date of publication

The subject identifier

A book is assigned between 1 and 3 letters and a whole number between 1 and 999 according to subject. There may also be a decimal extension to specify topic.

The item number

The item number consists of the initial letter of an author's name (or title in an edited work) followed by numbers read in decimal sequence.

Date of publication

This provides an additional aid to ordering books on the shelves.

It is important to remember that any number following a full stop should be read in decimal sequence as in the following example:


Most books in the Chemistry Library will be classified at QD (the subdivision for chemistry in the Q science schedule) or other subdivisions of Q such as QC (physics) or QP animal biochemistry. However, some titles may fall into other subject areas, for example, A (general works) or T (technology).

Outline of class Q Science

Q Science (general)
QA Mathematics
QB Astronomy
QC Physics
QD Chemistry
QE Geology
QH Natural History and Biology
QK Botany
QL Zoology
QM Human Anatomy
QP Physiology
QR Microbiology

Outline of class QD Chemistry

QD   1-999 Chemistry
  1-65 General (including alchemy)
  71-142 Analytical chemistry
  146-197 Inorganic chemistry
  241-441 Organic chemistry
  415-436 Biochemistry
  450-801 Physical and theoretical chemistry
  625-655 Radiation chemistry
  701-731 Photochemistry
  901-999 Crystallography

Example of notation display

For the following book title:

Levine, Raphael D.
Molecular reaction dynamics
Cambridge University Press, 2005

the Library of Congress call number will appear as:


- on the book spine,

and as

QD461.L66 2005

- in the library catalogue.

If there are any problems locating stock or interpreting LC classmarks please contact a member of library staff.