AKSEXICAL CATTLE DIPS. 3 



much of this water may evaporate with consequent destruction of 

 the crystalline form. The soda itself is in no way affected by this 

 loss of water, except that it really becomes stronger, weight for 

 weight. 



Another form of sodium carbonate, called " monohydrated sodium 

 carbonate," also occurs in commerce in the form of a white crystalline 

 granular powder. It contains only a small amount of water of 

 crystallization and is practically unaffected by exposure to air. This 

 form of soda from a manufacturing point of view is far preferable 

 to sal soda, as it is of constant and permanent composition, and 

 being much stronger, weight for weight, it is less expensive to handle. 

 When using monohydrated soda it is necessary to remember that 

 only 4^ pounds are needed to do the same work as 10 pounds of 

 sal soda. 



Pine tar. — Pine tar when fresh is semiliquid, but with age becomes 

 granular and nearly solid, in which condition it is of less value. 

 Mixed with it is always more or less water of decidedly acid prop- 

 erties (pyroligneous acid), which on standing tends to float on the 

 surface and should be dipped or poured off before the tar is used. 



Tar is heavier than water and when stirred with it usually forms 

 a very poor mixture from which most of the tar rapidly settles out, 

 but when the water is of just the right temperature and somewhat 

 alkaline a fairly stable suspension may generally be obtained. Wlien 

 previously treated with an amount of caustic alkali sufficient to com- 

 bine with a considerable proportion of the tar acids, or when blended 

 with soajj, the tar easily mixes with water and then forms a good and 

 permanent emulsion. 



Caustic soda. — Also known as sodium hydroxid, or sodium hydrate, 

 on account of its wide range of application by chemists, pharmacists, 

 and manufacturing industries occurs commercially in a number of 

 different forms, as powder, flakes, solid masses, or broken fragments ; 

 in color ranging from pure white to grayish or brownish tints. For 

 the use of chemists and pharmacists it is put up in glass bottles ; for 

 industrial purposes it is supplied in various sized cans or drums of 

 thin sheet iron. The latter is the variety that should be purchased 

 for making dip. Its large output and wide use render it easily 

 obtainable almost everywhere — far more so than white arsenic. The 

 10-pound can is the best size to buy for home use in preparing dips ; 

 larger consumers can probably handle the material in larger drums 

 conveniently and of course more economically. The purchaser must 

 make sure that the contents of the drum he contemplates buying are 

 in fragmentary form, or granulated, for much caustic soda is run 

 into drums in a melted condition and on cooling forms a single solid 

 cake, which, though satisfactory for factory use, is not adapted for 

 the present purpose. It should always be purchased under a guaranty 

 of not less than 85 per cent actual caustic soda. 



