Cattle-Fever Ticks. 23 



material becomes stronger, almost approaching vwnohydrated sodiwm 

 carhoncite. This latter substance is a coarse, granular powder, con- 

 taining only about one-seventh of its weight of water of crystalliza- 

 tion, and is very little affected by exposure to air. Sesquicarbonate of 

 soda is still another form which is stronger than sal soda, contain- 

 ing less than one-third of its weight of substances not actual sodium 

 carbonate. It is likewise little affected by air. 



Both monohydrated carbonate and sesquicarbonate dissolve readily 

 and can replace sal soda to excellent advantage provided their com- 

 position is guaranteed by a reliable firm. In calculating formulas 

 and costs it may be assumed that 10 pounds of sal soda can be re- 

 placed by 4^ pounds of the monohydrate or 5 pounds of the sesqui- 

 carbonate. 



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 usually more or less water of decidedly acid properties (pyro- 

 ligneous 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 generally may be obtained. Wlien 

 previously treated with caustic soda sufficient to combine with a con- 

 siderable proportion of the tar acids, or when blended with soap, the 

 tar easily mixes with water and then forms a good and permanent 

 emulsion. 



THE GENERAL COMPOSITION OF DIPS. 



All arsenical cattle dips contain arsenious oxid as the active tick- 

 killing agent. But since straight arsenious oxid — that is, white ar- 

 senic — is so slowly soluble in water, some chemical agent such as 

 sodium carbonate or hydroxid is necessary to bring it into solution. 

 In this way the white arsenic is changed to sodium arsenite. If cer- 

 tain manufacturing difficulties can be overcome it is possible that 

 sodium arsenite of reliable composition may appear later on the 

 market. Such a material could be dissolved directly in water and the 

 trouble of making the compound from white arsenic and caustic soda 

 would be avoided. 



But a plain water solution of sodium arsenite, however obtained, 

 does not make an entirely satisfactory dip. Better results follow 

 when pine tar is added. Possibly the pine tar increases the wetting 

 or spreading power of the bath, which naturally results in better 

 penetration and effectiveness against ticks and less risk of blistering 

 cattle. It is probable that the pine tar also makes the sodium arsenite 

 adhere better, so that it will less readily wash off in rain, or dust off 

 in dry weather. Perhaps it is distasteful to seed ticks so that they 



