The daily morning journal and courier., 1899-12-28

l periodic law. It seemed possible that one who had early seen some indica-
 tions of this law might, perhaps, also
 have discerned, even if obscurely, some
 principle relating to atomic weights l
 therefore once spent some time and
 pains in carefully reading the book,
 and considered at length those pas
 sages which, if any contained valid | criticism of the views which are gene l rally accepted.
 Hinrichs believes that the mean of
 series of determinations of an atomic
 weight cannot give the true value
 sought This proposition he deduces
 from a mathematical discussion. He 1 believes that as larger and larger quan-
 titles are taken in our analytical opera
 tions, the results differ regularly from
 ideal accuracy; sometimes the differ l ence continually increases as the quan- | tity taken increases, sometimes the diff | ference increases to a maxim and then
 decreases again. The proper computa-
 ton of an atomic weight, then accord | ing to Hinrchs consists, not in taking the mean of different observations,
 made with different weight of mate
 rials, but in determining the limit to- wards which the series conyergeS as
 the weight taken decreases. A good il-
 lustration is given: we cannot deter mine the weight of q new coin by
 weighing any number of old coins; ev- cry coin is worn, and therefore light and the mean weight of any number
 whatever is therefore necessarily below the mean weight of new cons But if | -,tr ola ntr afn hn In nfn
 of each, we may take the mean weights
 for each year separately, If we exam
 inc coins enough, these means when plotted as the ordinates with the years
 as abscissae, will give us fairly regular curve, lowest for the oldest
 coins, gradually rising towards a limit
 which they would not quite reach. This higher limit would evidently be the mean weight of a new coir."
 This is an intelligible proposition. It
 seemed to me worth while to examine
 it, for to this proposition one of the
 most enthusiastic and most active sup
 porters of Prouts hypothesis, a man
 not lacking in shrewdness or abaility
 or learning, has entrusted the defence
 of his favorte belief.
 lie dSSetlS llidl all dlclillN NGIS5 lth e'0
 determined by experiment is variable,
 that it depends on the amount of sub- stance taken for the analysis or other operation, and that it varies in a com tiuuous and regular manner. His prop
 osltion is, that an atomic weight as determined by experiment is a function of the weight of substance taken. Is
 there any evidence in favor of it2
 1 answer, first: Theory does not af-
 ford any evidence for it. Hlnrichs de- duces this proposition from theory by a discussion which is ma mathematical in form. Whether the proof is sound need not be considered, for his theory does not attempt to show the order of mag nitude of the regular and continuous variations which are affirmed to de- pend on the weight of substance taken and to show whether they can be sepa rated from the irregular and discon- tinuous errors due to accident We are sure that accidental errors exist; we may concede, for lgument, that regular and continuous varia ions also exist; but this is far from implying that the actual errors in given set of experiments will be largely or even peItEUllDlN OI tIG ldltbE klIu. | IlEDIN shows that there is a diurnal tide in the atmosphere; but theory does not show that the differences noted in a series of ten observations of the ba rometer at different hours of the day will follow the law of the diurnal tide.
 But, secondly: Facts do not agree with the proposition. The accidental errors of the most precise experiments yet made are so much greater than any systematic variations, that nothing but accidental variations can be de- tected. To prove this, let US consider Stas synthesis of silver nitrate from pure silver This is one of the most important determinations ever made. Hlnrchs has discussed it twice in his volume; he asserts that the ratio of sil yer nitrate to silver found in each an- alysis depends on the weight of silver taken, and twice draws curves to show this I assert, on the contrary, that the errors, which average only one part in forty thousand are purely accidental, and that they follow no law. This can be proved by proving that the ratios obtained depend on any other quanti- ties selected by accident just as much as they upptHu on IHe WelgntS or Sll- l. yer taken. Hinrichs plots the results of the ten determinations, using for ab- scissae the weights of silver taken, and so obtains tolerable curves. I plotted the same ten observations, using for abscssae, net the weights of silver taken but ten numbers selected sortes and get curves quite as to- erable as before; and this I did with ten different sets of abScissae all se- lected by pure accident. Now, quanti- ties which depend on any one of eleven sets of abscissae, ten of which are se- lected by accident are themselves ac- cidental in their variations and the facts are examined, they give no evil dence in favor of Hinrichs' proposition; We have seen that theory Is equally chary of her support, and we may safe ly dismiss the suspicion that any source of systematic errors can be detected in deducng atomic weights from the means of good experiments.
 Within the limits of convenience, it is well to vary the amount of substance , taken in analytical determinations. This has been a frequent practice in the fin $ est investigations. But that this prac- , tice derives any support from the so- ; called limit method" cannot be con , ,