Laboratory Analytical Methods

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  • Topic: X-ray crystallography, X-ray fluorescence, Diffraction
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Rock crushing, splitting samples, drying and grinding: Preparation for rock powder. Demonstrator: Encik Zamrut Daunar
Date (and venue): 28 July 2010 (Basement)
Aim: To crush, split, and grind solid sample rock for preparing rock powder. Objective:
1. To learn the techniques and mechanisms of preparing rock powder; which will be used as a sample for Bernas Bomb and XRF/ XRD techniques. 2. To know the processes and machines used in the rock crushing and sample preparation. Apparatus/ Machine: Hammer, face helmet (or goggles) and mask, rock powder container, plastic bag, spoon, gloves, labelling sticker and pen, cleaned Jaw crusher and TEMA Mill (i.e. laboratory disc mill). Material: Sample rock of Granite and Sandstone (hand specimen), Acetone. Procedure:

1. A piece of rock is selected (based on required size), cleaned and dried. 2. Using a sledgehammer, the selected rock sample is knocked into an approximately 5 to 10 cm in size (pebble-sized). For a hard rock (i.e. granite), a bigger sledgehammer is used while a smaller hammer is suitable for an easily breakable rock such as sandstone. 3. Coarser pieces of rock sample are kept in a plastic bag and labelled as (A). This sample can be used as a reference later. The remainders are placed into the jaw crusher before the machine is switched on. A person had to ensure that the remaining sample represents the whole rock (i.e. hand specimens). 4. After a few minutes of crushing, a little chunk of crushed rock is placed into a new plastic bag and labelled as (B). 5. The rest is taken out and placed into TEMA Mill in order to grind solid sample into powder form. In specific, rock sample is placed into a steel mould and for safety measure it is locked tightly in the grinding chamber (due to high vibration produced by an operated mill). It is left for about a minute. 6. Finally, the end powdery product is kept in another plastic bag and labelled as (C). This rock powder is relatively useful for further mineral/ element determination by various techniques (e.g. Bernas Bomb and XRF/ XRD techniques).

Discussion:
* Any machines used (i.e. Jaw crusher and TEMA mill) have to be cleaned at first, using high compressor air spray to prevent contamination of rock samples (by the leftovers of previous work) in order to acquire precise end-results. * Rock samples used need to be fresh rocks (without its weathered side) and cleaned (i.e. washed and dried in an oven at 60°C). Moreover, samples placed in the mould cannot be too overloaded in order to ease the grinding process by TEMA mill. * To prevent ‘scratching’ on the mould, a plastic spoon is used to remove/ place in the samples into the mould. Moreover, it also has to be cleaned using Acetone or rocks with high content of silica (i.e. granite); with traces of coloured sediments are the most difficult to be cleaned. These steps are important in order to avoid sample contamination. * Although ‘the longer TEMA mill operates the finer rock powder will be’, rock pieces cannot be left for too long during the grinding process as this might affect mineral content of the rock (i.e. due to excessive heat produced).

Figure A1: Crushing of rock sample using sledgehammer.

Figure A2: Steel mould and grinded rock powder.

Figure A3: Grinding chamber of TEMA mill.

Bernas Bomb technique: solution preparation for AAS (Atomic Absorption Spectrometer) and ICP (Inductively Coupling Plasma) determination. Staining of Feldspars
Demonstrator: Ms. Chia Yeng Choo
Date (and venue): 30 July 2010 (Geochemistry Lab)

Practical 1: Bernas Bomb (sample preparation for AAS and ICP) Aim: To ‘change’ sample material from solid to liquid form (i.e. solution) which later will be used in AAS and ICP methods for mineral determination. Objective: To prepare sample solution for AAS and ICP determination. Both sample preparation for ICP and AAS are similar in term of methods used but differ in term of sample...
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