ROCK PHOSPHATES.

Temuka Leader, Issue 5419, 26 July 1906, Page 3

ROCK PHOSPHATES.

The Government have pil.ilisned a pamphlet in connection wi:h the bonus that is being offered for Urn discovery of rock phosphates. It is compiled'by Mr 11. C. Aston. Chief Chemist in the Agricultural Department. Mr Aston points out that the prosi ncu of phosphates in the soil is essentia! to the growth of all crops, particularly root crops, such as turnips, mangolds, and potatoes. Many of the mils of this colony, especially ihose in the north, are deficient in phosphoric acid in amounts necessary for successfulturnip growing, and readily respond to an application of 2cwt to iewt of a phosphatic manure such as guano, bones, or superphosphate. Briefly, the following are the chief characteristics of the rock—(l) phosphates may have almost any colour, usually whitish, yellowish, greyish, ■greenish, pink or black. (2) Hardness—Softer than felspar or than quartz, bur harder than limestone. (3) Specific gmvi ty—Heavier than limestone, or quartz. J-l) Usually non crystalline, but may be crystalline. (5) Does not effervesce with acid. Mr Aston says a very good test that may bo applied by those who have the necessary materials is to grind the rock to a tine po'wdor, and place about as much will lie on n three-penny-bit, with about Ain of magnesium ribbon, in a glass tulje which has been drawn out and closed at one end, in the llarne. Tin; tube is then heated to redness over a lamp or candle, with a mouth blow-pipe, until the magnesium kindles, and then plunged into cold water. If any phosphate is present in quantity, a few bubbles of gas, consisting D t hydrides of phosphorus, will bo formed, and will communicate to the water and air a putrid metallic smell, which is most characteristic, and recalls the odour of decaying fish. This smell m a y often bo noticed near an acetylene generating plant. If a rock answering to the above description be found, a small specimen should in the first instance be sent per sample post addressed to the Chief Chemist, Department of Agriculture, Sydney street Wellington, by whom it will be tested and reported on free of charge.