LIVERPOOL chemists’ ASSOCIATION. 
585 
The microscopical structure of the teeth was then entered upon, and the chemical cha¬ 
racteristics of the various tissues discussed, viz. the enamel, dentine, and cenientum. The 
physiological relations of the dental organs to the nervous and sanguiniferous systems, 
together with a lucid description of the trifacial or fifth pair of nerves, w'ere given ; and 
the paper concluded with a notice of the alveolar processes, in which the teeth are 
situated, with their investing membranes of gum externally, and periosteum within. 
Numerous diagrams were employed to illustrate the paper, which was listened to with 
marked attention. 
Mr. Shaw, Mr. Robinson, Mr. Eedford, and others, expressed the gratification which 
they had derived from the clear and interesting paper of Dr. Waite ; and a vote of 
thanks was passed by acclamation. 
Ninth General Meeting, held February 28th; Mr. Redford in the chair, the Presi¬ 
dent being unwell. 
The minutes of the previous meeting were read and confirmed. 
The following donations to the Library were announced ;—Dr. Horace Dobell on 
Tuberculosis, by Mr. Charles Higgins. The Proceedings of the Liverpool Architectural 
Society. The Proceedings of the Liverpool Polytechnic Society. Mr. A. N. Tate pre¬ 
sented to the Museum a series of raw materials and products illustrating the manufac¬ 
ture of coal oil. Thanks w'ere voted to the donors. 
Mr. Redford asked the members for suggestions as to the best method of preventing 
steel apparatus from rusting during a sea voyage. 
Mr. Murphy proposed the use of chloride of antimony, as in browning gun-barrels. 
Mr. Robinson suggested packing in magnesia ; and Mr. Jones, coating with collodion. 
The President then called upon Mr. A. N. Tate, F.A.S.L., etc., of Mold, to read the 
paper for the evening, on “The Products of the Distillation of Cannel.” 
After giving a brief account of the processes by which the various products are ob¬ 
tained, Mr. Tate proceeded to describe the composition and properties of these products, 
and, in the course of his remarks upon the refined burning oil, said that the properties 
by which a mineral lamp oil are tested in the market are colour, smell, specific gravity, 
and point of ignition. Much importance is attached to colour, and the colour of an oil 
is certainly to some extent a test as to whether the oil has been properly refined or not; 
but a really good burning oil need not necessarily be colourless, as many persons sup¬ 
pose. The aim to make a perfectly colourless oil is a mistake in a manufacturing point 
of view, as it either necessitates too frequent distillation of the oil, or the rejection of a 
somewhat coloured but useful portion, which cannot be well used up as part of the 
other refined products. In order to obtain colourless oils, other more important proper¬ 
ties are overlooked or purposely neglected. The smell of an oil is a matter upon which 
few persons agree, but, of course, the less smell an oil possesses the less likely it is to 
prove objectionable in use. Burning oil, when newly made, has always a somewhat 
sharp pungent odour, but this becomes less as the oil grows older, so that the smell of 
an oil that has been kept some time is scarcely perceptible. The specific gravity has 
considerable effect upon the burning property. If too heavy, there is difficulty in get¬ 
ting the oil to rise properly through the wick; the wick becomes charred, the lamp 
smokes, and an inferior light is produced. If, on the hand, the specific gravity is too 
light, the oil is consumed too rapidly; but this, perhaps, is a point more for the conside¬ 
ration of the consumer than the producer. But there is also a certain relation between 
the specific gravity and the igniting point of an oil, and, as a rule, a low specific gravity 
indicates a low igniting point. The point of ignition is a point of very considerable 
importance, but the persons who use mineral lamp oil -know but little about it. The 
point of ignition is that temperature at which an oil throws off an inflammable vapour ; 
but perhaps this is not a sufficiently clear definition. Refined oils, like other liquids, 
throw off vapour even at a very cold temperature, but in such extremely small quantity 
as to be insufficient to form with the air in its vicinity an explosive mixture. But, as 
the temperature is gradually raised, a point is at last reached at which the oil gives off 
vapour at such a rate that, before it can be diffused away, it forms with the air in its 
immediate neighbourhood an explosive mixture, which will take fire immediatejy a flame 
is brought in contact with it. The temperature at which an oil commences to thus give 
ofi vapour is termed the igniting point. Neither crude cannel oil nor crude petroleum have 
a certain definite chemical composition, but consist of a number of hydrocarbons, pos- 
