30 ELEVENTH REPORT. 



INVESTIGATION ON THE TOXIC ACTION OF BORDEAUX 



MIXTURE. 



(Continued.) 



J. B. Daxdexo. 



This work is a continuation of that given before this section of the ]\Iich- 

 igan Academy of Science at the meeting of April, 1908, under the title of 

 "The Toxic Action of Bordeaux Mixture and of Certain Solutions on the 

 Spores of Fungi," and pubhshed in the tenth report, 1908, p. 57. In tlie 

 paper whose title has just been mentioned, it is stated that the Bordeaux 

 liquor problem needed further investigation in view of certain facts recorded 

 there. The most striking features of the mixtures which seemed to require 

 further research Avere, (1) That the sujiernatant liciuid was toxic to a very 

 considerable extent, when, according to the potass-ferro-cyanide test, it 

 contained no copper whatever; (2) That, in certain instances, the Bordeaux 

 mixture showed more toxicity in grades of solution more dilute (see tables 

 on page 60 of the report quoted above). One expects the toxicity to increase 

 as the strength increases. These two ideas gave rise to the investigation 

 given here below. 



The Bordeaux mixture was prejDared from the ordinaiy formula: o lbs. 

 copper sulphate; 4 lbs. lime, and 50 gallons water. This Avas the stock solu- 

 tion, and the various dilutions Avere made from this as follows: One-half, 

 one-fourth, one-eighth, etc. To test the toxic activity of the liquids, seed- 

 lings of pea. corn, and lupine were employed. For each test a sufficient 

 ciuantity (25 cc) for each seedling was used. It has already been demon- 

 strated by the writer* that a cjuantity of liciuid greater than 25 cc has no 

 further effect appreciable, consequently, for these seedlings, 25 cc represents 

 a ciuantity giving the maximum effect so far as ciuantity alone is concerned. 

 The radicle of each seedling was immersed for a distance of 20 mm or more 

 and allowed to remain immersed for at least 24 hours. The test of death 

 to the radicle Avas a groAA'th test. If the radicle grew in the reagent this was 

 held as conclusiA-e proof that the licjuid Avas not sufficiently toxic to kill it. 

 If the radicle did not grow, then it Avas concluded that death resulted. 



The supernatant liquor of the Bordeaux is of course a strong solution of 

 some compound of lime but properly contains no copper. This, Avhen titrated 

 AA'ith acid, shoAved a strength of lime of, ^/24.s or A'ery ajiiiroximately one- 

 twenty-fifth normal. It is interesting to note in connection Avith this strength, 

 that a saturated solution of lime (quick lime in Avater) at laboratory tem- 

 perature proved to be, on titration, ^/23, a solution only very slightly stronger 

 in lime than the supernatant Bordeaux liquid. 



The first set of experiments Avere made to determine at Avhat strength 

 the .supernatant liciuor might be and yet just permit groAvth of the radicle. 

 This supernatant liquor Avas siphoned from the stock Bordeaux after it had 

 been allowed to settle, and then diluted doAvn in fractions, one-half, one- 

 fourth, one-eighth, etc. The result of a number of experiments shoAved 



*.4merican Jour. Sci., June, 1904. p. 440. 



