Cone and quartering

Illustration showing the method of coning and quartering as a means of reducing a gross sample for subsampling, (a) The gross sample is first piled into a cone and... 

Ore samples are analyzed for %w/w Ni. A jaw crusher is used to break the original ore sample into smaller pieces that are then sieved into 5 size fractions. A portion of each fraction is reduced in size using a disk mill and samples taken for analysis by coning and quartering. The effect of particle size on the determination of %w/w Ni is evaluated. 

Coning and quartering is used to reduce the size of granular and powdered samples. The sample is placed on a flat surface in the form of a conical heap. The heap is then spread out and flattened into a circular cake, which is then divided into approximately equal quarters. One pair of opposite quarters is removed, combined and formed into a new cone for the process to be repeated (the other two quarters are discarded). The process is repeated as many times as is necessary to obtain a sample of the required size. 

A riffler is a mechanical device, consisting of a metal box containing a number of equally spaced slots, which is used for dividing a sample into two approximately equal portions. The material to be subdivided is poured into the top of the box and emerges through the slots on opposite sides in two approximately equal portions. As with coning and quartering, the procedure is repeated until the desired sample size is obtained. 

Particle size reduction is necessary to assure that various materials in the sample have roughly the same particle size [11]. Even after the particle size has been made reasonably uniform, the sample size has to be reduced to a manageable amount that can be analyzed, e.g., 0.5 g from a bulk sample of several kilograms in the example discussed above. Some of the approaches that have been used follow coning and quartering, proportional divider, and straight-line sampler (for details see Ref. [8]). 

Procedure. Take a representative of the bulk fertilizer sample and reduce in size by cone and quartering, or use a sample divider. Then grind and sieve to 0.2 mm (No. 70 or 70 mesh), mix thoroughly and immediately transfer to an airtight container. Weigh 0.0500 g (in duplicate) into a 50-ml micro-Kjeldahl... 

There are many laboratory devices available for the reduction of the primary sample to an analysis sample. The three most important methods used in the pharmaceutical industry are (i) scoop sampling, (ii) cone and quartering, and (iii) the spinning riffler or rotary sample divider (Fig. A-3). 

The dried fermentation residues were broken up to pass through a 6-mm screen and mixed three times by the method of cone and quarter mixing. The dried and screened HDG (-32 kg) was available for poultry-feeding trials (Table 3). The supernatant from the centrifugation step and filtrate from the filter belt were not evaporated to form concentrated syrup to be added to the dried HDG to form HDGS because of lack of pilot-scale equipment to accomplish the evaporation step. 

FIGURE 7 Subsampling (a) coning and quartering (b) table sampler [6] (c) oscillating hopper (paddle) sample divider [6] (d) spinning riffler (BSI) (e) riffle/chute splitter (BSI) if) revolving sample splitter [14]. 

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