U. S. EXPERIMENT STATION BULLETINS. 419 



single case of injury to health resulting from the daily absorption of small 

 quantities of copper was given. Many instances were cited, however, 

 where foods containing copper in considerable amounts were daily con- 

 sumed without any ill effects whatever. It is interesting to note in this 

 connection that notwithstanding the discussion before the Belgium academy 

 the law of July, 1882, prohibiting the use of copper in the re-greening of 

 fruits was repealed by the French authorities in the department of the 

 Seine. It appears, therefore, from all the evidence on the subject, that the 

 question under consideration is not settled by any means. For this reason 

 alleged cases of poisoning with copper should receive the most careful 

 investigation. 



We presume no one will deny that copper in large or even moderate 

 doses is unwholesome. Looking at the question from this standpoint, let 

 us consider the second part of our subject, i. e., Are the salts found in 

 sufficient quantity in connection with properly sprayed fruit, at the time of 

 harvest, to cause injury to health? At this point it may be well to add that 

 all our remarks apply to the Bordeaux mixture, which contains about 

 twenty times as much copper as the ammoniacal solution, the only addi- 

 tional fungicide worthy of consideration on account of its extended use. 



According to Gauthier, professor of chemistry of the faculty of medi- 

 cine. Paris, an adult can absorb daily for a period of several weeks without 

 ill effects from 0.2 to 0.5* grams of copper sulphate, or blue vitriol. Five- 

 tenths of a gram is usually considered the maximum amount that may be 

 absorbed for any length of time without injury to health, although cases 

 are on record where as high as 2, 3, and even 4 grams have been absorbed 

 for a number of days in succession without any ill effects whatever. Some 

 recent French investigations have shown that a dog can absorb from 15 to 

 25 grams of copper sulphate without injury. Sheep have been fed 43 grams 

 per day for several days in succession without any noticeable derangement 

 of the system. 



At this point we are confronted with a somewhat complex chemical 

 question which makes it difficult to obtain results strictly comparable. 

 The Bordeaux mixture as elsewhere shown, is made by the addition of lime 

 io a solution of copper sulphate. According to recent investigations, the 

 reaction is an exceedingly complicated one, the details of which are unnec- 

 essary here. It has generally been accepted that the mixture as sprayed 

 upon the vines consists for the most part of copper hydrate, which upon 

 •drying becomes an insoluble compound. We have, therefore, first of all. 

 the question to consider whether the hydrate is as likely to prove injurious 

 to health as the sulphate in solution. No direct investigations upon this 

 point have, so far as we know, been made. It has been shown, however, 

 that doses of copper four or five times greater can be administered in an 

 insoluble than in a soluble state. The question now briefly stated 

 resolves itself into this: May we, without assuming too much, use the facts 

 bearing on the harmfulness or harmlessness of copper sulphate when con- 

 sidering copper hydrate and copper oxide? We believe that this assump- 

 tion is not only admissible but is erring upon the safe side; in other words, 

 that if an adult can safely absorb 0.5 grams of copper sulphate a day with- 

 out injury, he may with much less fear of ill effects absorb the same quantity 

 ■of copper hydrate and copper oxide. In fact, as regards the ill effects of the 



* 1 gram equals 15.438 grains. 



