Available online
Description
Phase diagrams are a critical part of understanding how igneous rocks form - but are difficult to understand. This programme deals entirely with the construction and use of phase diagrams. D.A. Joh...nson, Lecturer in Chemistry, sets up a simple two component system from organic chemistry (Naphthalene and p-Nitrotoluene) to demonstrate how a simple phase diagram can be built up. Professor I.G. Gass extends this idea to three component systems. Step by step he constructs a 3 dimensional phase diagram using three binary eutectics. Having established the principles involved he shows how phase diagrams can contribute to our understanding of how igneous rocks form and with models he demonstrates both the basalt and granite systems.
Phase diagrams are a critical part of understanding how igneous rocks form - but are difficult to understand. This programme deals entirely with the construction and use of phase diagrams. D.A. Joh...nson, Lecturer in Chemistry, sets up a simple two component system from organic chemistry (Naphthalene and p-Nitrotoluene) to demonstrate how a simple phase diagram can be built up. Professor I.G. Gass extends this idea to three component systems. Step by step he constructs a 3 dimensional phase diagram using three binary eutectics. Having established the principles involved he shows how phase diagrams can contribute to our understanding of how igneous rocks form and with models he demonstrates both the basalt and granite systems.
| Item code: | S2-2; 04 |
|---|---|
| First transmission date: | 12-08-1972 |
| Published: | 1972 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:18 |
| + Show more... | |
| Producer: | Penny Crompton |
| Contributors: | Ian Gass; David Johnson |
| Publisher: | BBC Open University |
| Keyword(s): | 3-dimensional phase diagram; Basalt and granite formation; Binary eutectics; Igneous rock formation; Naphthalene and p-Nitrotoluene; Phase diagram construction |
| Footage description: | D.A.Johnson with laboratory apparatus for demonstrating phase change in organic chemicals - P-nitrotoluene and napthalene are used. Johnson monitors the temperature at which crystals form in the liquid napthalene. Johnson shows the cooling curve for a mixture of 75% napthalene and 25% p-Nitrotoluene. Graph axes are time/temperature. The temperature at which solid phase separates from the melt can be seen. Final freezing of the liquid is also shown. Shot of phase equilibrium diagram for Napthalene and p-Nitrotoluene. Johnson explains. Johnson with generalised form of a phase equilibrium diagram. He explains the components of the diagram. Johnson with a phase diagram for compounds which form mixed crystals (solid solutions). These compounds can form solid solutions over the whole range of compositions. Johnson explains the components of the diagram. Ian Gass constructs a model which can plot phase equilibrium for three components. This is a little closer to the situation of rocks forming from a melt. Gass plots a liquidus point for a mixture of a a given composition: A 10%, B 20%, c 70%. From this he can determine the liquidus surface for the 3 component system. The surface is contoured at 100 degree C intervals. Gass shows the phase diagram of the 3 component system above represented in 2 dimensions. He explains the components of the diagram. Shot of basalt rock formation. Shot of micrograph of a basalt sample. The two essential mineral crystals of the basalt are seen. Gass with phase diagram for basalt. He explains the components of the diagram. Gass shows a 3 dimensional model of the basalt system. He explains its components and then plots a melt point for a basalt with 60% Di and 40% An 50 composition. Gass shows what happens to the melt as Di crystals form and than when An 50 crystals form also. He explains what the model tells about the basalts. Shot of a granite-tor. Shot of micrograph of granite showing its three main components. Gass with a phase diagram for granite. He explains the components. Gass considers a melt of 60% Q, 30% Ab, 10% Or Composition. He plots the melt point on a 3 dimensional phase model and shows what happens as the melt cools. Gass explains what the model shows about the behaviour of granite. |
| Master spool number: | 6LT/70456 |
| Production number: | 00521_2161 |
| Videofinder number: | 1646 |
| Available to public: | no |
