ALGM 637 



tliem soft to tlie toucli. The mixture of tliao with gum traga- 

 canth is said to he the best method of using it, Thao should, 

 howeverj be used alone for materials which it is not necessary 

 should be stiffened. As thao is only soluble at a high terapera- 

 tu7*ej a moist atmosj)here, fog, or even rain does not affect the 

 material dressed with it. 



It combines well with sulphate of copper and the chlorides 

 of aniline and potassium, and can be used in double dyeing. 



It also answers well for sizing paper, &c. The only obstacle 



to its extensive use Is its high price. There is, however, no 



reason why a similar substance should not be made from our 

 common native sea-weeds, of which Gelideiim corneum and 



/^ 



character the 



algae from Avhich thao is made. G61ose, of which thao consists, 

 differs from the Carrageenin obtained from Chondrus crispus 

 in its power of combining with a very large quantity of water 

 to form a jelly ; it yields ten times as much jelly as an equal 

 weight of isinglass. For purposes of food, thao jelly is not 

 quite so pleasant as animal jelly, as it does not melt in the 

 mouth; it also contains no nitrogen. A great advantage 

 which it possesses is, that it is but little prone to undergo 

 change, so much so that the jelly is sometimes imported 

 from Singapore, under the name of sea-iveed jelly, sweetened, 

 flavoured, and ready for use, and may in this state be kept 

 for years without deterioration. Of late it has been much 

 used for the purpose of Bacteria culture, especially in warm 

 climates. 



Chemical composition.— ^ccordin^ to Payen, Gelose In a pure 

 state constitutes an immediate peculiar principle, insoluble in 

 alkaline solutions of soda, potash, and ammonia, as well as in 

 water, alcohol, ether, and dilute acids. One of its distinctive 

 characters, which Is quite peculiar, is that of dissolving slowly 

 iu a very small quantity of concentrated sulphuric or hydro- 

 chloric acid, which it colours brown, formi Jig with one or other 

 of them a brown compound, which gradually solidifies, and 

 ^Kich resists washing in cold or hot water, and even in caustic 



