819 



STRENGTH OF BEAMS. 



STRONTIUM. 



850 



Society, upwards of sixty varieties are "named as worth cultivating, and 

 there are as many, or perhaps more, which are reckoned worthless. 



Strawberries may be propagated either by means of their suckers or 

 runners, or by sowing seed. The young plants will generally bear the 

 year after they have been planted or sown. In order to obtain the 

 fruit in perfection, they should be planted where they have access to 

 abundance of light and air. Plants grown from runners are best for 

 new beds, and should be planted out in March, in beds with three or 

 four rows, leaving an alley between each bed. The alleys should be 

 wide, the beds kept clear from weeds, and the runners cut at least 

 three times in the season. In the autumn the rows should be dug 

 between, and in the spring some straw or dung should be laid between 

 the rows. If the manure produces too luxuriant a growth of the 

 plants, it should not be employed. The rows of the beds should be 

 two feet apart, the plants eighteen inches asunder, and the alleys three 

 feet wide between each bed. The duration of the plants is about three 

 years. As they are dioecious, care should be taken that there are male 

 plants in the bed in the proportion of about one to ten. The wood- 

 ttravbtrry is best produced from seed, which should be sown as soon 

 as it U obtained from the fruit, and should be planted in beds in 

 March, in the same way as the others. The alpine strawberry is best 

 grown from seeds, which should not be gown till the spring, and may 

 be planted in July or August, in rows at the back of hedges or walls, 

 in a rich or moist soil The duration of these and of the last seldom 

 exceeds two years. 



Strawberries, when ripe, may be eaten in almost any quantity with- 

 out injury. They are frequently eaten mixed with sugar and cream, 

 or, wine. When ripe and well grown, they hardly require such additions ; 

 but wEen their sugar is deficient, this ingredient may be safely added ; 

 and the addition of wine under these circumstances should be preferred 

 t > cream, as the latter is very liable to disagree with disordered 

 stomachs. 



STRENGTH OF BEAMS, PILLARS, 4c. [MATERIALS, STRENGTH 

 or.] 



STRINO-C'OUKSE, a projecting course of masonry forming a string 

 i IT horizontal line ou the face of a wall, and consisting of a series of 

 moulding)), as in Gothic, or of a flat surface (either plain or enriched), 

 an in Italian architecture. In both styles, string-courses admit of great 

 variety, and contribute very much to decoration, while they are in 

 themselves essential members, inasmuch as they serve to define the 

 internal division of the building, corresponding with the floors of the 

 several stories ; and by separating one tier of windows from another, 

 to mark each as a distinct portion of the general composition, complete 

 as regards itself, though secondary to the other. While they separate, 

 they serve also to connect and combine the successive stages of a 

 building; and to produce a due admixture of horizontal with per- 

 pendicular lines. 



STRONTIA. [STRONTIUM.] 



STllO'NTIUM (Sr). A peculiar metal found in combination with 

 oxygen and carbonic or sulphuric acid, and forming the carbonate and 

 sulphate of strontia. From the very considerable resemblance existing 

 between baryta and strontia they were once supposed to be 1 identical. 

 Crawford and Sulze noticed a difference between them, and in the year 

 1 7' 1 - Dr. Hope established sufficient differences to prove that they were 

 completely distinct bodies, and the newly discovered body was named 

 ,NV ; -., ,!//, or Strontittt, from Strontian in Scotland, the place in which 

 it was discovered. 



Strontium was procured from the carbonate of strontia by Davy in 

 1808 ; the method adopted is that which we have described for obtain- 

 ing barium [BARIUM] from the carbonate of baryta. It is a malleable 

 metal of a pale yellow colour, is heavier than sulphuric acid, fixed, 

 difficultly fusible, and not volatile. When exposed to the air it attracts 

 oxygen, and becomes converted into strontia ; when thrown into water, 

 it decomposes it with great violence, producing hydrogen gas, and 

 forming with the water a solution of strontia. 



itn and Strontiam, as just mentioned, readily unite, constituting 

 the protoxide, or itrvntia (SrO), which in combination with acids exists 

 largely in nature, and the peroxide, which is entirely an artificial pro- 

 duct. The amplest mode of procuring the protoxide, or strontia, 

 when required to be free from water, is to dissolve the native carbonate 

 in nitric acid, and to decompose the crystallised nitrate obtained at a 

 red heat ; or the sulphate of strontia, which is a much more common 

 substance, may be converted by the well known means first into sul- 

 phide and then into nitrate. The properties of strontia are, that it 

 has a grayish-white colour ; its specific gravity is between 3 and 4 ; it 

 it very infusible, not volatile, has an acrid taste, and has an alkaline 

 reaction on vegetable colours. On comparing these properties with 

 those of baryta, it will be observed that there is considerable resem- 

 blance between them, but they difi'er in one remarkable respect, 

 namely, that strontia, unlike baryta, is not poisonous. When exposed 

 lir it attracts carbonic acid, and is reconverted to the state of 



. l- ','.!! I*--. 



filr'/ntta and Water combine to form at least two compounds : when 

 a small quantity of water is |>oured upon strontia, it slakes, gives out 

 heat, is rendered white, and becoming a hydrate, it is fusible at a 

 white heat, but does not part with its water. Its formula in SrOHO. 



According to Davy, utrontia is soluble in about two hundred times 

 its weight of water at common temperatures. The solution is called 



ARTS ASD CI. DIT. VOL. VII. 



Strontia Water, and is occasionally employed as a chemical reagent; 

 it acts energetically as an alkali on vegetable colours and in saturating 

 acids. In boiling water strontia is much more soluble than in cold. 

 As the solution cools, crystals, the primary form of which is a square 

 prism, are deposited, and these appear to consist of SrO, 9HO. 



Peroxide of Strontium (Sr0 2 ) may probably be obtained, as the per- 

 oxiue of barium is, by passing oxygen gas over strontia at a red heat, 

 or by heating it with chlorate of potash. 



Neither nitrogen nor hydrogen unites with strontium. 



Chlorine and Strontium, combine to form only one compound, con- 

 sisting of (SrCl). 



The best mode of procuring this salt is to dissolve carbonate of 

 strontia in dilute hydrochloric acid, and to evaporate the solution to 

 its crystallising point, the chloride containing water then separates in 

 long slender crystals, which consist of one equivalent of chloride and one 

 equivalent of water. When exposed to heat the water is expelled, and 

 a solid white chloride remains. The crystals deliquesce in a moist 

 atmosphere, are soluble in twice their weight of water at 60", and still 

 more so in boiling water ; this salt is soluble also in alcohol, and the 

 solution when burning exhibits the peculiar red flame characteristic of 

 the compounds of this metal. 



Chloride of strontium may be more directly, but less eligibly, pre- 

 pared than in the mode now described, by passing chlorine gas over 

 heated etrontia; oxygen gas is expelled, and chloride of strontium 

 remains. 



Fluoride of Strontium (SrF) is an insoluble pulverulent compound. 



Sulphide of Strontium (SrS) may be formed either by heating the 

 native sulphate with charcoal, or by fusing strontia and sulphur in a 

 green glass tube. It dissolves in hot water, and as the solution cools 

 crystals of sulphide of strontium are formed. They appear to contain 

 water. 



This compound is used for the preparation of the salts of strontia, 

 the sulphate being a much more common substance than the carbon- 

 ate, which is preferable however when obtainable. 



We shall now describe three oxisalts of strontia, two of which exist 

 in nature, and the third is occasionally employed in chemical re- 

 searches. 



Carbonate of Strontia; Slroniianite. This was the first discovered 

 compound of strontia; it occurs crystallised and massive. Primary 

 form, a right rhombic prism. Cleavage, parallel to the lateral faces of 

 the primary form. Fracture, uneven. Hardness, scratches carbonate 

 of lime, but is scratched by fluor-spar. Colour, white, greenish, gray- 

 ish, and brown. Streak, white. Lustre, vitreous. Transparent, trans- 

 lucent. Specific gravity 3'605. 



Before the blow-pipe it fuses, and gives a purple light. It dissolves 

 with effervescence in dilute nitric acid, and the solution is precipitated 

 by sulphuric acid. 



Manire Varieties. Amorphous, globular. Structure fibrous, some- 

 times granular. 



Found at Strontian in Scotland, Brauusdorf in Saxony, and in Peru. 



Analysis by Klaproth : 



Carbonic acid . . SO 4 



Stnmli.l . . 09-5 



Water ... 0-5 



100- 



Stromnite, or Baryslronlianite, or Barytiferous Carbonate of Strontia, 

 is a mineral found at Stromness in Orkney. It occurs massive. Struc- 

 ture fibrous. Hardness 3'5. Specific gravity 3*7. Lustre somewhat 

 pearly. Translucent on the edges. Colour grayish and yellowish 

 white. It is soft and brittle. Effervesces with acids, but does not 

 melt before the blow-pipe. 



According to Dr. Traill, who discovered this substance, it con- 

 sists of 



Carbonate of etrontia 

 Sulphate of baryta 

 Carbonate of lime . 

 Oxide of iron 

 Loss 



08-6 



27-5 



2-G 



0-1 



I'i 



100- 



Carbonate of Strontia (SrOCO.,) may be artificially obtained by 

 several processes ; as by exposing strontia water to the air, or by 

 adding an alkaline carbonate to it ; or by decomposing any soluble salt 

 of strontia, by means of an alkaline carbonate, &c. In whatever mode 

 obtained, it is a colourless insipid powder, quite insoluble in water, 

 decomposed by acids with effervescence, and by exposure to a high 

 temperature. It is used for preparing the various salts of strontia. 



^nljihate of Strontia; Celettin. Exists largely in nature. It occurs 

 crystallised and massive. Primary form a right rhombic prism. 

 Cleavage easy, parallel to the base of the primary form, but less so 

 in the direction of the lateral faces. Fracture conchoidal, uneven. 

 Scratches carbonate of lime, but it is scratched by fluor-spar. It is 

 brittle. Colour white, bluish, reddish-white. Transparent; trans- 

 lucent. Lustre vitreous. Specific gravity 3'858. 



The Masnive Varieties are nodular, tabular, and amorphous. Struc- 

 ture columnar, fibrous, granular. 



3 I 



