PIPES. (In confectionery.) These are formed from any of the common lozenge-masses, by rolling them into cylinders of about the thickness of a goose-quill. They are frequently medicated.
PIPETTE. A graduated glass instrument, in frequent use in the chemical laboratory, for conveying a measured quantity of fluid from one vessel to another. The pipette mostly consists of a bulb, from each end of which proceeds a straight, slender hollow stem, communicating with the bulb, and varying in length with the capacity of the instrument. Thus constructed, the lower end of the pipette can be dipped into a vessel with a narrow and long neck, such as a flask, containing a fluid, the required volume of which can be removed from it. The pipette varies in capacity from 1 to 200 cubic centimètres.
Dr Fresenius gives the following directions for its use:—“To fill a pipette with the fluid which it is intended to transfer from one vessel to another, the lower part of the instrument is dipped into the fluid, and suction applied to the upper aperture, either direct with the lips or through a caoutchouc tube until the fluid in the pipette stands a little above the required mark; the upper, somewhat narrowed, ground orifice is then closed with the point of the index of the right hand, which to that end had always better be moistened a little, and holding the pipette in a perfectly vertical direction, the excess of over the quantity required is made to drop out by lifting the finger a little. When the fluid in the pipette has fallen to the required level, the drops which may happen to adhere to the outside of the pipette are carefully wiped off, and the contents of the tube are then fully transferred to the other vessel. In this process it is found that the fluid does not run out completely, but that a small portion of it remains adhering to the glass in the point of the pipette; after a time, as this becomes increased by other minute particles of fluid trickling down from the upper part of the tube, a drop gathers at the lower orifice, which may be allowed to fall from its own weight, or may be made to drop off by a slight shake; if, after this, the point of the pipette be laid against a moist portion of the inner side of the vessel, another minute portion of fluid will
trickle out; and lastly, another trifling droplet or so may be got out by blowing into the pipette through the upper orifice. Now, supposing the operator follows no fixed rule in this respect, letting the fluid, for instance, in one operation simply run out, whilst in another operation he lets it drain afterwards, and in a third blows off the last particles of it from the pipette, it is evident that the respective quantities of fluid delivered in the several operations cannot be quite equal. I prefer in all cases the second method, viz. to lay the point of the pipette whilst draining finally against a moist portion of the inner side of the vessel, which I have always found to give the most accurate corresponding measurements.”
PISTA′CHIO NUTS. Syn. Pistacia nuts; Nuces pistaciæ, L. The kernels of the fruit of Piscatia vera (Linn.), one of the turpentine trees. They closely resemble almonds, but are sweeter, and form a green emulsion with water. Used in confectionery and perfumery, and also as a dessert fruit.
PITCH. Syn. Black pitch, Boiled p., Stone p., Wood p.; Pix (Ph. L.), Pix nigra, L. “A dry bitumen prepared from liquid pitch.” (Ph. L.) The residuum from boiling tar in an open iron pot, or in a still, until the volatile and liquid portion is driven off. The volatile products principally consist of crude pyroligneous acid and oil of tar. Pitch is chiefly employed in ship-building. As a medicine, it is stimulant and tonic, and has been used internally in some skin diseases, and in piles. An ointment made of it is also extensively used in cutaneous affections of the scaly.—Dose, 10 gr. to 1⁄2 dr.
Pitch, Burgundy. Syn. White pitch, Burgundy pine resin; Pix Burgundica (B. P., Ph. L., E., & D.), L. “Impure resin prepared from the turpentine of Abies excelsa,” or Norway spruce fir. (Ph. L.) “A concrete resinous exudation, probably, in a great measure, from Abies excelsa.” (Ph. E.) It is chiefly used in plasters.
Obs. The importation of this substance has for some years past been gradually lessening in amount, in consequence of the substitution for it of a fictitious pitch, made by melting common resin with linseed oil, and colouring the mass with annotta or palm oil. The physiological action of the two articles is, however, considerably different, since Burgundy pitch acts upon the skin as a powerful local irritant, exciting a slight degree of inflammation, and not unfrequently producing a pimply eruption and an exudation of purulent matter. It is celebrated for its effects when employed as a plaster in all cases where warmth, support, and long adhesion to the skin, are desirable; and in the latter quality no substance equals it. The fictitious Burgundy pitch has similar properties, but in an immensely less degree.
Prepared Burgundy Pitch (Pix Burgundica præparata—Ph. L.) is ordered
to be obtained in the same way as that adopted for strained ammoniacum. This plan is, however, seldom, if ever, adopted in trade.