Errors, common

Why would a knowledgeable scholar like Porta reinforce incorrect information such as that heating of antimony produces lead Scientific experimentation was still only in its infancy. Early writers such as Pliny often turned folklore into fact. In his book Pseudodoxia Epidemica Or, Enquiries Into Very Many Received Tenents, and Commonly Presumed Truths the physician Thomas Browne notes on page 83  

And first we hear it in every mans mouth, and in many good Authors we reade it. That a Diamond, which is the hardest of stones, and not yielding unto Steele, Emery, or any thing, but its own powder, is yet made soft, or broke by the bloud of a Goat  

Goat s blood softens a diamond so that it can be shattered Browne refers to this vulgar and common error and notes that, while some scholars accepted it, diamond cutters, whom we can presume as unscholarly, knew it was not true. He traces the misconception to the notion that in order to produce such potent blood, some scholars wrote that goats must be fed certain herbs that were said to dissolve kidney stones in humans. Since kidney stones are also extremely hard and can be broken, why not diamonds  

Thomas Browne, Pseudodoxia Epidemica Or, Enquiries into Very Many Received Tenents, and Commonly Presumed Truths, T.H. for Edward Dod, London, 1646. I thank my daughter Rachel Greenberg for bringing goat s blood and diamonds to my attention. 

Where could we have gone astray here Most often, it is forgetting a crosscheck. 

We could have done the previous mechanism in one step with four arrows, but that would assume a three-molecule collision, something that is very rare. The arrows would not involve the C=0, which is essential for the reaction to proceed. This reaction goes through a resonance-stabilized intermediate, the stability of which we can check. Made-up combinations of arrows are hard to check and may just shift the lines and dots of our Lewis structure without saying anything chemically understandable. For our mechanistic sentences to make sense we must use known words, the electron flow paths. 

Biochemical Note An enzyme s active site can have weak acids and bases close to our reactant. It is often possible to have proton transfer occurring in the same step as another electron flow path. These are discussed separately in Section 7.4.3. 

In our mechanism example, we could have started off on an impulse to do an acidic mechanism in basic conditions. What would have caught us was our first A eq crosscheck. Using ethanol as an acid (pAfa = 16), the most favorable ATeq we could have gotten would have been protonating the carbonyl lone pair at 10 , which is not usable. We would be saved by our crosscheck. Generally a good rule is In acid protonate the reactant, and in base deprotonate it. 

A shorthand notation you may see in some texts is to drop a proton off by itself or show a naked proton being picked up by a base. Under the conditions found in almost all 

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The viscous or frictional loss term in the mechanical energy balance for most cases is obtained experimentally. For many common fittings found in piping systems, such as expansions, contrac tions, elbows and valves, data are available to estimate the losses. Substitution into the energy balance then allows calculation of pressure drop. A common error is to assume that pressure drop and frictional losses are equivalent. Equation (6-16) shows that in addition to fric tional losses, other factors such as shaft work and velocity or elevation change influence pressure drop. 

Most often, the Mach number is calculated using the speed of sound evaluated at the local pressure and temperature. When M = 1, the flow is critical or sonic and the velocity equals the local speed of sound. For subsonic flowM < 1 while supersonic flows have M > 1. Compressibility effects are important when the Mach number exceeds 0.1 to 0.2. A common error is to assume that compressibihty effects are always negligible when the Mach number is small. The proper assessment of whether compressibihty is important should be based on relative density changes, not on Mach number. 

MOST COMMON ERRORS FOUND ON FORM R REPORTS... 

One of the most common errors made at the process-flow-diagrara stage is failure to foresee that flow may take place in the reverse direction to that intended, as diseussed next [1]. 

Proper condensate removal is important. An inverted split cup inside the shell, with the upper capped end above the nozzle and the lower open end -in. above the bottom tubesheet, should be used to cover the oudet nozzle. This can be made by splitting a pipe that is one size larger than the condensate oudet down the centerline. In this case, a 2-in. split is adequate. This cup must be fully seal welded (not tack welded) to force condensate down to the -in. clearance above the bottom tubesheet. A common error is to allow 6 in. or more above the tubesheet for the centerline of the condensate oudet. In this case, 6 in. of tube is 10% of the surface. If the cup is not used, add 10% more tubes to correct for the dead liquid space near the bottom. This is in addidon to the 10% safety factor. 

Data recording One of the most common errors made with this technique is reversing the 3 and 9 o clock readings. Technicians have a tendency to reverse their orientation to the machine train during the alignment process. As a result, they often reverse the orientation of the recorded data. 

A common error is to confuse the GPC distribution with the weight distribution. The response of a refractive index detector is proportional to the mass of polymer. The GPC elution volume (V) typically scales according to the logarithm of the degree of polymerization (or the logarithm of the molecular... 

A note on good practice F.xponential functions are very sensitive to rounding errors, so it is important to carry out the numerical calculation in one step. A common error is to forget to express the enthalpy of vaporization in joules (not kilojoules) per mole, but keeping track of units will help you to avoid that mistake. 

Common errors in research management, indicating the most likely needs for simulations to provide practice in decision making and give feedback on a range of possible outcomes... 

Mahmoudi A, Iseman MD. Pitfalls in the care of patients with tuberculosis Common errors and their association with the acquisition of drug resistance. JAMA 1993 270 65-68. 

Excerpts from Ortus medicinae, Id est, initia physicae inavidita. Progressus medicinae novus, in morborum, ultionem, ad vitam longam. .. (Amsterdam Elzevir, 1648), translated by John Chandler (as Oriatricke, or Physick Refined, the common Errors therein Refuted..., London 1662, 1664) and reprinted in Henry M. Leicester Herbert S. Klickstein, A Source Book in Chemistry, 1400-1900"... 

Helmont, Jean Baptiste van. Oriatrike, or physick refined. The common errors therein refuted, and the whole art reformed and rectified being a new rise and progress of phylosophy and medicine, for the destruction of diseases and prolongation of life. Written by that most learned, famous, profound, and acute phylosopher, and chymical physitian,. 

There are several practical scaleup lessons with heterogeneous catalysts in batch slurry reactions. One often uses four times the catalyst concentration in the lab to achieve the same results in the plant reactor. Plant charge is 1 wt. part for 1000 wt. part, where as in the lab one uses 5 grams or more per 1000 grams. A common error is the confusion between wet (gross) weight and dry weight (net)... 

Another common error in the preparation of this mobile phase is the use of industrial grades of ethanol, which contain uv-absorbing impurities. The source of the ethanol should have been specified as well. 

Maintenance errors. One common error is the failure to remove an isolation blind in a vent line when returning a vessel to service. Even a thin sheet of plastic placed over an open nozzle may be sufficient to allow a vessel-damaging vacuum to De produced (BP, Hazards of Trapped Pressure and Vacuum, 2003). 

Pictorial models are a helpful part of documenting a design. Unfortunately, it is a common error to treat the pictures as the sole focus of documentation or design activities. Teams spend a real lot of money on modeling tools, draw lots of pictures using these tools, and then expect to press a button to generate well-structured, clear, explanatory documentation. Sadly, it does not usually turn out exactly that way. 

This error message comes up when something does not calculate correctly, such as dividing by zero. This is a common error that occurs when equations contain a variable in the denominator that is initially zero. Often it is possible to add a very small number to it, so that the denominator is never exactly zero. These cases can usually be located by outputing a table of all the variables. 

The probit distribution is derived form a common error function, with the mid point (50% point) moved to a score of 5.00. 

The most common error made in colligative property problems is to forget to separate the ions of an electrolyte. The van t Hoff factor, even when not needed, is a useful reminder. 

Spend time on your rough draft. Organize your essay so it moves logically from paragraph to paragraph, and understand your audience and what they are looking for. Use each part of the essay, introduction, body, and conclusion effectively, and avoid common errors that can weaken your writing. 

A few dozen grammar, spelling, punctuation, and capitalization mistakes account for the majority of common writing errors. Once you become acquainted with these common errors and learn how to avoid or correct them, your writing will greatly improve. Therefore, this section on mechanics will focus on the errors that occur most frequently. 

Four of the eight major parts of speech represent the majority of usage difficulties. Learning these common errors will help you avoid them and instead write more clear, concise sentences. 

In addition to helping to convey your voice and personality, commas are often used misused. There are two common errors that all college-bound students should be aware of the comma splice, and the serial comma. 

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