Y EL
ZE O
( 495 )
which is left at firft. in the cloth, hut goes off byfhort expofure to the air.
M. Achard diftilled per fe in a retort oneounce of wool, with a heat gradually increafedto ignition. There was left in the retort 2fdrams of a coaly refidue ; the neck of the retortwas lined with a black fhining foot; beyondwhich was a faline fublimate ; and in the re-ceiver was about 2 drams of an empyreumaticoil, together with fome neutral ammoniacalfait, the nature of which was not afcertained.
WOOL Fbilofophical. See Zinc.
WORMWOOD, Salt of.
The purer kinds of fait of tartar or carbonatof potalh were often termed fait of wormwood,particularly in medicine, the allies of this plantyielding an abundance of this aikaii. See Car-bonat of Potajh.
WORM-TUB. A part of the common dif-tilling apparatus. (Sc? the Appendix .)
WOULFE’s APPARATUS. (See the Ap-pendix. )
W JRFELSPATH. See Anhydrous Sele-nite, p. 547. Vol. 1.
Y
YEAST. See Fermentation.
YELLOW (Naples).
The Naples Yellow { Giallolino ) Is a fine pig-ment long prepared at Naples, which has theappearance of an earth, is very friable, heavy,porous, not alterable by expofure to air, and ofa pale orange-yellow colour.. When heated itexhales no fenfible vapour, melts when red-hot,but undergoes no other change except that thecolour becomes deeper. Boiling water andacids extrafb a portion from it, but do not dil-folve it entirely.
This pigment (the preparation of which iskept fecret) has been examined by feveralchemifts, but no accurate analyfis has beenmade of it. Fougeroux {hewed that it was ametallic oxyd by reducing it with a proper flux,and eafdy obtained a regulus from it, whichconfifted of lead and antimony. 1 Beckman andCouret have confirmed this compofition. Aprocefs which produces a fimilar pigment isthus given by Couret. b Mix together 12 oz. ofcerufie, 3 oz. of diaphoretic antimony, ofalum and fal-ammoniac each one ounce, heat
them for a confiderable heat below rednefs, andafterwards in a red heat for three hours longer,,after v/hich the mafs will have acquired a beau-tiful yellow colour.
The Giallolino is little employed in this-country, its ufe being fupplied by Turner’sPatent Telloiu, prepared from Lead in the man-ner delcribed under that article.
YELLOW EARTH. Gelberde y Wern.Terre jaune, Broch.
Its colour is ochre-yellow; it occurs in mafs;it is dull or at moft feebly glimmering. Itsfrafture in the great is flaty, but in fmall is fine-grained earthy, pairing into imperfectly con-choidal. It is very foft, almoit friable; itacquires a polilh by fritHon; ftains the fingers,and is iomewnat undtuous to the touch, it ad-heres flightly to the tongue, and is of littlefpe.cific gravity.
It is employed in the arts as a pigment.
It forms beds in clay, and iromloue, atWehrau, in Upper Saxony.
z
ZEIc.H£NSC dIEFER. SeeTHONscmF.FER.
ZEOLITE. Zcolith, Wern.
Of this mineral th.re are the three followingfubfpecies.
1 . Subfp. Radiated Z. Strahliger, Z. Wern.jl defotype, Hauy.
Its colour is yellowifh-white, greyifh, reddifliand fnow-white. It occurs maffive, globular,and cryftallized. Its primitive form is a rectan-gular, tetrahedral prifm: fometimes the prifm
0 Mem 4 e l’Acad. for 1766.
is terminated by tetrahedral pyramids, the bale?of which correipond with the taces of the prifm:fometimes the prifm is comprefied, and termi-nated by tetrahedral pyramids let on the lateraledges of the prifm;, the lummits of the termi-nal pyramids are allb often truncated. Thecryftais are middle-fized and fmall, and ofterrlaterally aggregated, fo that their fummits aloneare diitinguithable : the lateral pianes arefmooth and fhining. Internally it is glifiening^with a pearly luftre. Its fracture is divergingly1 J. Piiyf. Toax xxxvi.