Bituminous Materials – Solubility Check for Purity/Grading In bitumen testing for road construction, which solvent is used as the reference medium in which standard paving bitumen is considered completely soluble under normal test conditions?

Introduction:
Solubility tests help indicate purity and type of bituminous binders. The exam focus is on the standard solvent used historically to confirm complete solubility of bitumen as part of identification/quality control for paving grades.

Given Data / Assumptions:

• Material: petroleum bitumen used in road works.
• Goal: identify the solvent in which bitumen is completely soluble for routine checks.
• Laboratory context: classical tests and references used in specifications.

Concept / Approach:

Classical material science texts and road specifications consider bitumen completely soluble in carbon disulphide (CS2). Other solvents may dissolve appreciable portions, but CS2 has been the accepted reference solvent for complete solubility checks.

Step-by-Step Solution:

Verification / Alternative check:

Older IS/ASTM style texts cite CS2 solubility as a defining property; modern environmental practices may use other safer solvents for routine handling, but conceptually CS2 remains the classical reference.

Why Other Options Are Wrong:

Chloroform/benzene: not the canonical “complete solubility” reference for bitumen identity. Coal tar: not a solvent; it is a distinct binder. “All of the above” is incorrect because the standard reference is CS2.

Common Pitfalls:

Confusing coal tar with a solvent; assuming any aromatic solvent implies complete solubility in the sense required by the standard identity test.

Final Answer:

Carbon disulphide (carbon bisulphide)