Document JJOQp39j0qM1edre9wGgr2bm2

-l-9i 1955 Mr. Lawrence ?. Fairhall Barvarcl b'nive: -s.ity School of Public Health ^5 '-ian Byke Street Boston, Maas. Lear Mr* Fairhall: Allow to thank you again for your Invitation to come to your laboratory at a later date* I am ai'raid, however, that it will be impossible for some to come, and I wish to repeat my invitation for you to come here* X believe that the whole matter would he greatly facilitated by |iour doing this since we are carrying on a considerable volume of work of this type at present, and since you will therefore be able to See what you will on the minutest details of our work. My plans at present are such that I do not see how I can absent myself from the laboratory. I shall be teaching until well into the middle of June., after which time.*- X have some three or four engagements out of town which I can not avoid. I have made plans to begin my vacation on or about July 1st, and since thse involve the plans of a number of other people as well as my o w n , I can not conveniently modify them. Xt would be quite convenient for us to have you here any time during the next six \veeks, and I shall be very glad to have you come. With regard to your use of acetic acid, I must confess that my conclusion that you employed 2 c.c. basic acetic acid in excess was arrived at somewhat indirectly. Your description of your method has not Included a state ment as to the precise amount of acid employed, while your data regarded in checking the me'hod has referred repeatedly to the use of such amounts. I naturally inferred that this representated your customary procedure. I should like also to remark that it is only when the amounts of lead in the samples are less than half a milligram that substantially quantitative precipitation falls to occur. Amounts above this are usually percipitated quantitatively even in the presence of an acidity represented by 2 c.c, of glacial acetld acid in excess. When the amounts are as low as one tenth of a milligram, there is usually not the slightest evidence of turbidity or of any percitptatlon at this acid concentration. M9593