AT THE MATERIAL:

It has tried to consider as more as possible Marcelin's shrewdness, using industrial synthesis oleic acid ad hexane; the lycopodium seed was foreign matter-free and extra-fine-grained, the bowl enough large to contain (after the first fiascoes) the spot, but surely the first element having qualitatively distort misurements was the use of Bolognese tap water: it has a percentage of melted salts higher than the national average, particularly Ca²⁺, Na⁺, SO₄^2-, CO₃^2- which could have influenced the result in two ways.

For one thing ions near the water surface and probable foreign matter have surely been affect the spread of the spot and its thickness; even more generally they may have helped the solution of some oleic acid's or hexane's apolar molecules.

AT THE 3 THEORETICAL DATA:

Adequately accurate even if not checked, they have been got from source in the public and global-authority net, like wikipedia, the Nist… which however not associating them errors have made us in fairness explicit them overrated higher was the influence they had on the final result (see for example the oleic acid's molar mass), still without being able to use them in propagation.

AT THE INSTRUMENTS:

Laboratory instruments have turned out to be enough accurate and sensitive for our need, although it has been necessary to go beyond the simple secondary-school propagation of errors propagazione as noone between sensivity errors was negligible compared to the average linked: we will discuss it again within some paragraphs; whereas as far as the last and most remarkable instrument is concerned, we devotes it the next one.

AT THE PROCEDURE AND AT THE 4 EXPERIMENTAL DATA:

Among a lot of trials carried out it was considered only the final one with the smallest number of systematic errors linked instead of an average of all those ones made, along of the inner heterogeneity of the correctness's degree and not so much of the type of the single passages.

Systematic errors done during this one have whatever been qualitatively a lot, again they haven't affected in a quantitatively-heavy way (for the first significant figure) nor least of all detectable: so here it will be tried to set them in order by time and at the same time by growing importance.

First of all the bowl's filling and transport haven't been realized so ably to prevent that the swinging water wetted the vat, to flow again after with the lycopodium already sprinkled.

The lycopodium scattering has been repeated again and again, but without succeed in avoid the forming of some little lump and the presence of some square millimetre in areas where it was absent: it contributed thereto the imperceptible convection of the water in the tank.

Being both the hexane and oleic acid concave-meniscus liquids (they damp the vat's wall because of the preponderance in the liquid of the interaction with the vat's wall on the internal one) it has been easier slightly underrating the final solution's density since in the several pouring off drops of liquid (particularly oleic acid) have surely sticked on the graduated cylinder's sides.

Then they come the most influential errors in the most critical phase: it has been sought for holding the pipette's bill on the water's surface to avoid as much as possible the final solution forcefully bouncing or surfacing on the water with likely fragmentations and approach to the rim: that besides enabled to make light of (but not to cancel absolutely) the quantity of tiny little bubbles wandering “semimelted” in the water conceivable as spheres whose radii were oleic acid's molecules with the hydrophilic C1C9 and C14C18 arms bent as always on the surface of contact with water and the hydrophobic one C10C13 on the bubble's core. As it happens with air or steam bubbles, big bubbles would be swiftly bring back to the surface because of the density lower than water one, whereas the smaller ones would be restrained for a longer time because of the relative greater strength of the interactions with water and because of the internal streams. The amount of solution missed in this way has slightly lowered the volume value as regards the rated one, raising even more slightly the final result value.

The lycopodium on the other hand being effectively apolar (hydrophobic) upsets the surface of the water, soaking up instead the final solution: that surely (as it's manifest in the photo) brought about besides the formation of lumps, certainty the incorporation by the spot of lycopodium grains, but especially the spot-thickness's non-molecularity near the grains, hence undervaluating the surface in a way appreciable in the final result.

In conclusion the mark's area has come in for random errors at the time of its estimate from the photo: calculation has been performed with a visuale approximation to the little square, but previously, the spot not having clear boundaries, pixels with a such brown color tipical of lycopodium have been blacken, without counting that the wet one incorporated came out lighter and nearer to the oleic acid's color.

AT THE CALCULUSES:

Here they are concentrated the inaccuracies underlying the non-concurrence of the Avogadro's constant real value with that one finally obtained by us.

At first it must be observed at the method's level that in order to get the mark's surface and its error, such as generally for the propagation of errors, it has been used the semidifference. They have been neglected some statistical hard-grasp shrewdness.

So the standard deviation (with its propagation) would have allowed us to attain outcomes surely more accurate, but then again this one should have come after the experimental shrewdness, for not coming out negligible or even misleading; even more evidently, it would have obscured with the enormous bulk and intricacy of extra computation the laboratory trial's primary popular aims of clearness and easy access for an unexpert public, already tough to satisfy with some eminently scientific elements already introduced at the secondary-school.

Likewise it would have been for the squaring propagation, one potential middle course which isn't usually showed at school, and which to fulfil fully its synthesis potentiality would require the explanation for example of the concept of squaring sum.

Well let's go to the practice of elaboration, where beyond the inaccuracy in considering tetrahedra and triangles as regular (actually bringing back to the distance C-C also the distances C-H, C-O e O-H), to mainly affect they have been the approximation of the oleic acid's molecule to an elliptical based cylinder: in our defence it goes the the fact that there aren't other models with comparable simplicity which last by comparison, and that much visible empty space is effectually created by the intermolecular bond distances (Van der Waals's forces). More exactly, the model of ellipse proposed is of course arbitrary but as much easy as possible and, as already clarified in situ, we have duly and uprightly connected to semiaxes an error so high as ensuring the belonging of the "real" elliptical surface's measure to the proposed interval.