UME-SULFUR-SALT MIXTURE 643 



bonate is changed to sodium or potassium bicarbonate. Add 

 methyl orange and continue the titration to the appearance of 

 a pink color. This reading (m) represents the sodium or po- 

 tassium bicarbonate present or one-half of the sodium or potas- 

 sium carbonate ; 2m represents all the sodium or potassium car- 

 bonate present, and n-m the sodium or potassium hydroxid. 



538. Discussion of Methods of Analysis of Caustic Soda and 

 Potash. By Method I higher results are always obtained for- 

 soclium hydroxid than by Method II, while by Method I lower 

 results are always obtained for sodium carbonate than by Meth- 

 od II. Although Method II is somewhat more difficult than 

 Method I because of the great care necessary in reading the two 

 end points, Haywood is inclined to think that it is somewhat more 

 accurate for the following reasons : In Method I after the car- 

 bonates are precipitated out by barium chlorid, the supernatant 

 liquid is titrated for the hydroxid present. Since barium car- 

 bonate is soluble to quite an extent in water that portion which is 

 soluble is also titrated as hydroxid, thus increasing the hydrox- 

 id figure. In Method II all the hydroxid and one-half the car- 

 bonate are first titrated, then the other half of the sodium car- 

 bonate, so there does not seem to be the same chance of error. 



539. Lime-Sulfur-Salt Mixture. The lime-sulfur-salt mixture 

 or simply the lime-sulfur mixture without the salt is very large- 

 ly used in this country against the San Jose scale. On account 

 of the trouble incident to its home preparation it has of late 

 years appeared on the American market in a concentrated form. 

 The chemist is often called upon to examine this concentrated 

 mixture in order that the entomologist may calculate the proper 

 dilution. 



It has been shown by Haywood that the liquid portion of the 

 lime-sulfur-salt wash, which is the portion sold on the market, 

 when prepared by any of the formulas ordinarily employed, con- 

 sists principally of sulfids and polysulfids together with a moder- 

 ately large quantity of thiosulfates and very small quantities of 

 sulfates and sulfites. 21 It is therefore necessary to make the fol- 

 lowing determinations on a commercial sample of the lime-sul- 

 " Bureau of Chemistry, Bulletin 101, 1907. 



