FREEZING MACHINE 



3338 



FREIBURG- IM-BREISGAU 



separated from the Baptist body, 

 which at that time was strongly 

 Calvinistic, and taught Arminian 

 doctrines. See Baptists ; Calvinism. 



Freezing Machine. Double 

 pail for making ice-cream. Ice and 

 salt, broken very small, are packed 

 into the outer pail in layers of 

 three inches of ice and one of salt 

 nearly to the top. The cream mix- 

 ture is poured into the central pail, 

 which is provided with a dasher, its 

 handle passing through a hole in 

 the top ; this is turned until the 

 mixture is set. See Ice Cream. 



Freezing Mixture. Mixture of 

 two substances, usually ice or snow 

 and some kind of salt, which pro- 

 duces great cold. When common 

 salt is added to snow which is on 

 the point of freezing, its first effect 

 is to lower the freezing point of 

 that part of the snow with which it 

 is brought into immediate contact ; 

 some of the snow is accordingly 

 melted and forms a strong solution 

 of salt. In this solution the mole- 

 cules of water and of salt enjoy 

 much greater freedom of motion 

 than in the solid form, and require 

 extra energy, which is provided in 

 the form of great heat from the 

 surroundings. Thus the tempera- 

 ture of the snow is reduced below 

 its normal freezing-point, and at 

 the same time the saline solution 

 melts more snow, this process con- 

 tinuing until a limiting low tem- 

 perature is reached at which the 

 whole mixture freezes. A tem- 

 perature of 20 C. can be reached 

 in this way with a mixture of snow 

 and common salt, but by the use of 

 other salts which dissolve with 

 greater absorption of heat much 

 lower temperatures can be ob- 

 tained. For example, calcium 

 chloride in its crystalline form, 

 mixed with snow in the proportion 

 of 10 parts to 7, will produce a tem- 

 perature of 55 C. 



Freezing Point. Temperature 

 at which a liquid assumes the solid 

 form. The freezing point of water, 

 that is, the temperature at which 

 it changes into ice, is one of the 

 fixed points on the thermometric 

 scale (0 Centigrade, 32 Fahren- 

 heit). Liquids may be roughly di- 

 vided into two classes as regards 

 the properties they exhibit in the 

 process of freezing ; water is an 

 example of the liquids which under- 

 go crystalline solidification, in 

 which there is a change of volume, 

 and the liquid gives out a definite 

 quantity of heat, called the 

 " latent heat," in its abrupt change 

 to the solid form. On the other 

 hand, molten glass is a liquid 

 which undergoes " amorphous " 

 solidification ; as the temperature 

 falls the glass ceases to run freely, 

 and becomes viscous, then gradu- 



ally hardens into a solid. The 

 second class of liquids can hardly 

 be said to have a definite freez- 

 ing point, although the correspond- 

 ing solids have a melting point, 

 namely, the temperature at which 

 they begin to run. 



To return to the first type, in 

 which freezing is an abrupt change, 

 it is a fact of great importance that 

 the freezing point is not absolutely 

 constant, but varies under pres- 

 sure. Water expands when it 

 freezes, and the effect of pressure 

 is to lower the freezing point. 

 Paraffin wax, on the other hand, 

 contracts in freezing, and here the 

 effect of pressure is to raise the 

 freezing point. In other words, 

 those liquids which can solidify only 

 by expanding, are hindered from 

 freezing by external pressure, while 

 those which have to contract in 

 order to freeze are helped by ex- 

 ternal pressure. 



The freezing point of a liquid is 

 lowered by the presence of a salt 

 dissolved in it. Thus a solution of 

 common salt in water will not 

 freeze until its temperature has 

 been lowered considerably below 

 the freezing point of pure water. 

 The reason for this appears plainly 

 from the molecular theory. Ac- 

 cording to this theory the mole- 

 cules of water, which in the liquid 

 form have considerable freedom of 

 movement, have 

 to occupy definite 

 relative positions 

 when the water 

 assumes the form 

 of ice. When pure 

 water is cooled to ; 

 C., the energy 

 of the molecules is 

 sufficiently dim- 

 inished to allow 

 attractive forces 

 to come into play, 

 under which the 

 molecules assume 

 the positions re- j 

 quired for freez- 

 ing, but the pre- 

 sence of particles 

 of salt in the 

 solution hinders 

 this process, and 

 the energy of 

 the molecules of 

 water must be 

 diminished by a 

 further reduction 

 of temperature be- 

 fore solidification 

 can take place. 

 See Heat; Tem- 

 perature ; T h e r 

 mometer. 



Freiberg. Town 

 of Germany, in 

 Saxony. It stands 

 on the river Munz- 



bach, a tributary of the Mulde, 

 20 m. S.W. of Dresden, and is tho 

 mining centre of the Erzgebirge. 

 Around are extensive silver and 

 lead mines, while the town itself has 

 an old and celebrated school of 

 mines. Other industries are the 

 manufacture of textiles, iron and 

 brass goods, cigars, thread, chemi- 

 cals, beer, and gunpowder. The 

 chief building is the 12th century 

 Gothic cathedral, restored in 1893, 

 and containing a famous doorway, 

 called the Golden Door, which has 

 some magnificent sculptures. 



S. Peter's church is noteworthy, 

 and there are remains of the town 

 walls, parts of which have been 

 turned into promenades, a museum, 

 a park, and several public monu- 

 ments. The town grew up around 

 the castle of Freudenstein, which 

 became a residence of the dukes of 

 Saxony. One of them rebuilt it in 

 the 16th century, and this building 

 remains. The silver mines, to which 

 the town owes its existence, were 

 opened about 1250. Pop. 36,237. 



Freiburg. Small country town 

 in Silesia. It is built upon a hillside, 

 36 m. S.W. of Breslau. There are 

 manufactures of linen and watch- 

 cases. Pop. 9,800. 



Freiburg-im-Breisgau. Town 

 of Germany, in Baden. It stands 

 on the Dreisam, near the western 

 borders of the Black Forest, 40 m. 



Freiburg-im-Breisgau. The early Gothic cathedral with 

 famous 13th century tower, 386 ft. high 



