Hazel-nut-oil (FR., Hulle de Noisettes).—The hazel-nut (see p.1358) affords about 60 per cent. of oil, which, in some parts of continental Europe, is extracted by pressure, in the same manner as almond-oil. It is limpid, clear-yellow in colour, and of sweet and agreeable flavour ; it congeals at —19° (-2° F.) [some say at —10° (14° F.)] ; has a sp. gr. of 0.924 at 15° (59° F.) ; and soon becomes rancid. Its chief application is for perfumery. Other wild species in India and elsewhere probably yield similar oils.
Hempseed-oil (FR., Nude de Chanvre, de Clahnevis; GER., Hanf61).—The seeds of the hemp plant, so well known as a fibre-producer (see Fibrous Substances, p. 934), are valued for their oil. It is from Russia and Lorraine that the seed for expressing mostly comes. When the fibrous stems are tied in bundles, the seed is rudely threshed out, and spread in thin layers under cover to dry. The extraction of the oil is performed in the same manner as with other seed-oils, described in a separate section of this article (see p. 1451). The proportion of oil contained in the seed is about 34 per cent. on an average ; the yield varies from 25 to 30 per cent. The oil is at first greenish- or brownish-yellow, deepening with exposure to the air ; the flavour is disagreeable, and the odour is mild. It has a sp. gr. of 0'9252 at 15° (59° F.); it thickens at —15° (5° F.), and solidifies at —25°— (7 F.); it dissolves in 30 parte of cold alcohol and any proportion of boiling ; it saponifies with difficulty, forming a soft soap, but less soft than that from linseed-oil. It is locally consumed largely for lighting, but its most important application is for making soft-soaps. The exports of hempseed from Riga were 21,011 quarters in 1875, and 78,690 in 1878; and in 1879, 725,809 poods (of 36 lb.) of the seed, and 573 of the oil. In 1872 (the date of the latest return), Russia had 812,630 acres under hemp, which yielded 14,410,000 bush. of seed. In France, 238,100 acres under hemp in 1874 produced 1,263,424 bush. of seed.
Hickory-nut-oil.—From the seeds of several species of Carya (see Nuts, p. 1358), excel lent oil for illuminating and lubricating purposes has been extracted in Ohio. It continues fluid at very low temperatures, and is used for delicate machinery, and even for watches, when refined. The pig-nut (C. glabra) is preferred, on account of its thin shell and greater yield of oil, which is bitter. The oils from the " shell-bark " and the large sweet hickory-nut are very palatable, and might come into table use.
Horse-chestnut-oil (Fe., Male de Marron d' Ade, de Fecule).—The whole fruit of the horse chestnut (see Nuts pp. 1352-3) contains two fixed oils, one in the case, which is and a second in the kernel, of an orange-yellow tint. The proportion of oil in the kernel is very small. Chemists have detected by analysis a quantity varying from 3 to 5i per cent., reckoned upon the green kernels ; but the highest yield obtained in practice has been 11 per cent, even when treating 2 cwt. at a time. Nevertheless some hundreds of cwt. of the oil have been made in France, chiefly by Emile Genevoix, a Parisian druggist. He employs the unpeeled kernels, and proceeds by destroying the starch present by boiling them with water acidulated with sulphuric acid, and collecting the oil which floats upon the surface. He remarks that the production of the oil is certain only when acting upon large quantities, that the water plays an important part in the operation, and that every precaution is necessary to prevent the oil being saponified during the process. The fresh oil seen in bulk is greenish-brown, with an empyreumatic odour, and a peculiar flavour ; these qualities are intensified by age. It is remarkably slow to become rancid, and may be kept almost indefinitely. On the Continent, it has a great reputation as a cure for gout, rheumatism, and neuralgia.
I]lipi-butter.—The almond-like fruit-kernels of Bassia longifolia afford a semi-solid fat. The tree flourishes in Malabar and on the Coromandel coast. The seeds contain about 30 per cent. of oil, 121 lb. of them yielding about 2 gal. of oil by the ordinary rude native way of expressing. The oil will not keep for more than 2-3 weeks in the Indian hot season ; it then becomes rancid, and emits a disagreeable odour. When well secured from contact with the air, it will keep for some months in cool weather. Its colour is usually bright-yellow, varying somewhat according to the care used in preparing it. It is eaten as a substitute for ghee, is burnt in lamps, and is employed in the manufacture of country soap, and for external medical application. The cakes left after the expression are used for washing the head, and form an article of trade. Fats from other species of Bassia are described under Mahwa-oil (p. 1394), Phulwara-oil (p. 1408), and Shea-butter (p. 1410).