An improved method for the automated determination of urine calcium.
The problems of accurately determining urine calcium are described. The basic technique described is little changed from that originally used by Clark and Collip but the pitfalls encountered when applying this to automated procedures are demonstrated and a means of overcoming them proposed.
EVALUATION OF PROCEDURES FOR URINARY CALCIUM.
In a comparative study of urinary calcium methods, many of the recently proposed procedures proved either impractical or invalid in our hands. A preliminary isolation of the calcium as the oxalate, followed by perchloric acid oxidation of the oxalate seemed to be the simplest procedure whereby urinary calcium could be put in a state suitable for chelometric titration. The isolated calcium could also be titrated with considerable precision and accuracy by a modified procedure with a derivative automatic titrator which is available commercially.

It was suggested from our observations that too little attention has been directed towards the problems imposed by the occurrence of calcium precipitates in urine. An untreated 24-hr. urine specimen is not suitable for direct analysis of calcium by chelometric titration, by colorimetric analysis, by emission flame photometry, or by atomic absorption flame photometry because these methods do not give a true measure of the calcium in the precipitate. Boiling for 5 min. with 1 part concentrated nitric acid to 25 parts urine proved a suitable means for completely dissolving the calcium precipitate.
Hedy: A Gradual Language for Programming Education
One of the aspects of programming that learners often struggle with is the syntax of programming languages: remembering the right commands to use and combining those into a working program. Prior research demonstrated that students submit source code with syntax errors in 73% of cases and even the best students do so in 50% of cases. An analysis of 37 million compilations by 250.000 students found that the most common error was a syntax error, which occurred in almost 800.000 compilations. It was also found that Java and Perl are not easier to understand than a programming language with randomly generated keywords, stressing the difficulties that novices face in understanding syntax. This paper presents Hedy: a new way of teaching the syntax of a programming language to novices, inspired by educational methods by which punctuation is taught to children. Hedy starts as a simple programming language without any syntactic elements such as brackets, colons or indentation. The rules slowly and gradually change until the novices are programming in Python. Hedy is evaluated on 9714 programs.