Fluorides sentence example
At the same time Berzelius obtained the element, in an impure condition, by fusing silica with charcoal and iron in a blast furnace; its preparation in a pure condition he first accomplished in 1823, when he invented the method of heating double potassium fluorides with metallic potassium.
It forms many double salts with other metallic fluorides.
Its double salts with the alkaline fluorides are very important, and serve for the separation of the metal from columbium and titanium.
The salts of hydrofluoric acid are known as fluorides and are easily obtained by the action of the acid on metals or their oxides, hydroxides or carbonates.
The fluorides of the alkali metals, of silver, and of most of the heavy metals are soluble in water; those of the alkaline earths are insoluble.Advertisement
A characteristic property of the alkaline fluorides is their power of combining with a molecule of hydrofluoric acid and with the fluorides of the more electro-negative elements to form double fluorides, a behaviour not shown by other metallic halides.
Fluorides can be readily detected by their power of etching glass when warmed with sulphuric acid; or by warming them in a glass tube with concentrated sulphuric acid and holding a moistened glass rod in the mouth of the tube, the water apparently gelatinizes owing to the decomposition of the silicon fluoride formed.
The atomic weight of fluorine has been determined by the conversion of calcium, sodium and potassium fluorides into the corresponding sulphates.
Dufour' discovered that the lines into which the band spectra of the fluorides of the alkaline earths may be resolved widen towards the red under increased pressure.
His work included investigations of osmic acid, of the ferrates, stannates, plumbates, &c., and of ozone, attempts to obtain free fluorine by the electrolysis of fused fluorides, and the discovery of anhydrous hydrofluoric acid and of a series of acides sulphazotes, the precise nature of which long remained a matter of discussion.Advertisement
As a part of the voltage is consumed in the latter duty, only the residue can be converted into chemical work, and as the theoretical voltage of the aluminium fluoride in the cryolite is 4.0, provided the bath is kept properly supplied with alumina, the fluorides are not attacked.
The bromides closely resemble the chlorides and fluorides.
Mixed metal oxides and phases containing mixed anions, such as oxide fluorides, provide our current focus.
It is the principal inorganic constituent of bones, and hence of the "bone-ash" of commerce (see Phosphorus); it occurs with fluorides in the mineral apatite (q.v.); and the concretions known as coprolites largely consist of this salt.
It forms a series of double fluorides, the most important of which is cryolite; this mineral has been applied to the commercial preparation of the metal (see above).Advertisement
Systemic fluorides, including fluoridated water and prescription fluoride supplements supplied as tablets, drops, or lozenges, can be incorporated into the enamel of children's developing teeth.
Topical fluorides are applied directly to the surfaces of fully-formed teeth.
Other topical fluorides include fluoridated toothpastes and mouthwashes and fluoride gels that are applied to children's teeth at dental examinations.
Thus topical fluorides help prevent decay in both children and adults.
Systemic fluorides also can provide topical protection because they are incorporated into the saliva that bathes the teeth.Advertisement