HEATING OF HAY.

New Zealand Herald, Volume LXVII, Issue 20562, 13 May 1930, Page 14

HEATING OF HAY.

SPONTANEOUS COMBUSTION

Loss of hay through firo liaS been unusually heavy .this season, a fact which is attributed mostly to causes promoted bv tJio stacking of hay in a damp condition, which, in turn, was due to tho unfavourable weather. Interest, attaches to an opinion, lately expressed by Dr. Browne, of the United States Department of Agriculture, Washington, on tho question of spontaneous combustion. After reviewing tho efforts made for hundreds of years to solve the, matter, ho summarises, the present knowledge of tho subject and emphasises tho urgent need for further study of the problem which he, regards as one of tho most important in tho whole field of agricultural research.

It is well known, Dr. Browne oxplains, tliat tho primary step in (.lie heating of liay is duo in large part to enzymic and bacterial- action, which causes a breaking down of tho carbohydrates and other substances of the stored material. This is commonly known as fermentation or decay. * Iheso vital processes, however, are mostly destroyed by heat at about 150 degrees Fahrenheit, and tho riso of teinpcraturo from this point to tho 600 degrees or inoro necessary for ignition, has been a puzzling problem of chemistry.

Dr. Browne's theory is tli.it bacteria produce certain unstable, unsaturated compounds which by their gre iter affinity for atmospheric oxygen raise tne temperature not only U> tho death point of tho bacteria, but to the point of ignition. Tho process is purely chemical, and is comparable to the familiar examplo of spontaneous ignition of cotton waste when coated with an unsaturated substance such as linseed oil.

Dr. Browno explains that gaseous, products formed in tho intcr'or of a heating stack exert an outward pressure from tho centres of chemical activity, or socalled " hot-pcckots," 'creating flutn or channels. 'When such a flue caches tho surf aco of tho stack there is a sudden inrush of air to tho hot pocket. Tho ensuing oxidation of tho hot rinsat.ural.ed products of bacterial decomposition causes such a riso in temperature that ignition readily takes place. In casi' tho pressure of gases is insuflieienl to open a passage for tho entrance of large volumes of outside air, oxidation proceeds at a much slower rate, and there is only a charring of tho hay without ignition.

A determination of tlu; exact chemical processes involved in spontaneous healing is necessary for the development of effective storage methods for farm products to reduce loss from lire or spoilage, says Dr. Browno. He emphasises Iho need for exf.ensivo co-operative experiments on the subject by chemists, bacteriologists, and engineers.