BIOLOGICAL EXAMINATION OF DISTILLED WATER. 2O I 



From the above and other experiments I can make the state- 

 ments enumerated below, which apply, of course, to Arbacia only 

 but point to the necessity of caution in using distilled water on 

 other organisms. It is true also that the results are most appli- 

 cable to Woods Hole conditions and to the tap-water used as a 

 basis of the distilled water there. It is probable that the toxicity 

 is due to ammonia although this was not proven. It is certain 

 from experiments made that Arbacia larvae are very sensitive to 

 that substance. 



1. Tap-water is decidedly, although variably, toxic. The 

 toxicity is not lost by sterilization but is greatly reduced by boil- 

 ing the water for a long time, say until one third has been boiled 

 away. The residue in such cases is less toxic than some distilled 

 waters, particularly commercial brands and that from automatic 

 stills. 



2. Water from ordinary automatic stills, whether metal or en- 

 tirely glass, is toxic. 



3. The commercial distilled waters used by me were toxic, 

 often in high degree. 



4. In distilling water in the ordinary way from glass, the first 

 one tenth distilled over is decidedly toxic, the second tenth less 

 so, the third tenth still less so. The fourth tenth is of good 

 quality. 



5. The best distilled water used was produced by double dis- 

 tilling in glass, the first fourth distilled over in each distillation 

 being rejected. 



6. Nearly as good water was produced by single distillation 

 from tap-water to which H 2 SO 4 and K 2 Cr 2 O 7 had been added. 



7. If a little H 2 SO 4 is added to the tap-water to start with, an 

 excellent quality of distilled water may be produced from an 

 automatic still consisting of a copper vessel and glass condenser, 

 the arrangement being such that none of the condensed water 

 touches the metal. This water is practically free from ions or 

 toxic volatile substances. It is much better than water double 

 distilled in glass in the ordinary way, unless in the later case a 

 large proportion of the product be thrown away. Such an auto- 

 matic still is recommended for use at Woods Hole. 



8. It was noted in a number of cases that Arbacia lived longer 



